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	$56.35	11.639%	$62.9086	$62.91	$62.90	$62.90
Purchase #2	$53.88	4.236%	$56.1624	$56.16	$56.15	$56.20
Purchase #3	$247.31	8.674%	$268.7617	$268.76	$268.75	$268.80
Purchase #4	$122.34	6.565%	$130.3716	$130.37	$130.35	$130.40
Purchase #5	$124.35	13.444%	$141.0676	$141.07	$141.05	$141.10
Purchase #6	$242.82	5.243%	$255.5511	$255.55	$255.55	$255.60
Purchase #7	$141.35	4.341%	$147.486	$147.49	$147.50	$147.50
7 purchase totals =	$988.40		$1,062.3090	$1,062.31	$1,062.25	$1,062.50