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	$47.74	12.794%	$53.8479	$53.85	$53.85	$53.80
Purchase #2	$35.94	3.345%	$37.1422	$37.14	$37.15	$37.10
Purchase #3	$109.33	12.666%	$123.1777	$123.18	$123.20	$123.20
Purchase #4	$133.93	11.339%	$149.1163	$149.12	$149.10	$149.10
Purchase #5	$176.31	4.663%	$184.5313	$184.53	$184.55	$184.50
Purchase #6	$32.48	7.319%	$34.8572	$34.86	$34.85	$34.90
Purchase #7	$65.59	3.561%	$67.9257	$67.93	$67.95	$67.90
7 purchase totals =	$601.32		$650.5983	$650.61	$650.65	$650.50