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	$134.91	9.463%	$147.6765	$147.68	$147.70	$147.70
Purchase #2	$223.79	6.412%	$238.1394	$238.14	$238.15	$238.10
Purchase #3	$165.72	3.729%	$171.8997	$171.90	$171.90	$171.90
Purchase #4	$12.91	3.217%	$13.3253	$13.33	$13.35	$13.30
Purchase #5	$50.57	11.716%	$56.4948	$56.49	$56.50	$56.50
Purchase #6	$194.56	13.449%	$220.7264	$220.73	$220.75	$220.70
Purchase #7	$148.39	4.609%	$155.2293	$155.23	$155.25	$155.20
7 purchase totals =	$930.85		$1,003.4914	$1,003.50	$1,003.60	$1,003.40