Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$153.90	4.689%	$161.1164	$161.12	$161.10	$161.10
Purchase #2	$159.47	12.130%	$178.8137	$178.81	$178.80	$178.80
Purchase #3	$181.40	8.335%	$196.5197	$196.52	$196.50	$196.50
Purchase #4	$194.48	12.508%	$218.8056	$218.81	$218.80	$218.80
Purchase #5	$167.52	10.735%	$185.5033	$185.50	$185.50	$185.50
Purchase #6	$186.82	4.615%	$195.4417	$195.44	$195.45	$195.40
Purchase #7	$111.57	12.723%	$125.7651	$125.77	$125.75	$125.80
7 purchase totals =	$1,155.16		$1,261.9655	$1,261.97	$1,261.90	$1,261.90