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	$125.40	6.417%	$133.4469	$133.45	$133.45	$133.40
Purchase #2	$7.54	13.310%	$8.5436	$8.54	$8.55	$8.50
Purchase #3	$147.46	8.133%	$159.4529	$159.45	$159.45	$159.50
Purchase #4	$156.70	10.134%	$172.58	$172.58	$172.60	$172.60
Purchase #5	$161.43	3.525%	$167.1204	$167.12	$167.10	$167.10
Purchase #6	$125.81	13.135%	$142.3351	$142.34	$142.35	$142.30
Purchase #7	$86.48	6.172%	$91.8175	$91.82	$91.80	$91.80
7 purchase totals =	$810.82		$875.2964	$875.30	$875.30	$875.20