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	$155.72	11.116%	$173.0298	$173.03	$173.05	$173.00
Purchase #2	$149.55	4.626%	$156.4682	$156.47	$156.45	$156.50
Purchase #3	$133.36	9.293%	$145.7531	$145.75	$145.75	$145.80
Purchase #4	$153.89	7.409%	$165.2917	$165.29	$165.30	$165.30
Purchase #5	$200.25	9.809%	$219.8925	$219.89	$219.90	$219.90
Purchase #6	$195.46	11.707%	$218.3425	$218.34	$218.35	$218.30
Purchase #7	$168.54	11.298%	$187.5816	$187.58	$187.60	$187.60
7 purchase totals =	$1,156.77		$1,266.3594	$1,266.35	$1,266.40	$1,266.40