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	$119.30	10.447%	$131.7633	$131.76	$131.75	$131.80
Purchase #2	$168.86	13.292%	$191.3049	$191.30	$191.30	$191.30
Purchase #3	$236.32	11.848%	$264.3192	$264.32	$264.30	$264.30
Purchase #4	$167.65	4.477%	$175.1557	$175.16	$175.15	$175.20
Purchase #5	$248.93	5.468%	$262.5415	$262.54	$262.55	$262.50
Purchase #6	$53.35	3.355%	$55.1399	$55.14	$55.15	$55.10
Purchase #7	$149.69	8.843%	$162.9271	$162.93	$162.95	$162.90
7 purchase totals =	$1,144.10		$1,243.1516	$1,243.15	$1,243.15	$1,243.10