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	$107.75	9.780%	$118.288	$118.29	$118.30	$118.30
Purchase #2	$22.78	11.550%	$25.4111	$25.41	$25.40	$25.40
Purchase #3	$111.68	10.264%	$123.1428	$123.14	$123.15	$123.10
Purchase #4	$139.97	7.658%	$150.6889	$150.69	$150.70	$150.70
Purchase #5	$69.41	10.542%	$76.7272	$76.73	$76.75	$76.70
Purchase #6	$147.51	13.322%	$167.1613	$167.16	$167.15	$167.20
Purchase #7	$106.31	4.817%	$111.431	$111.43	$111.45	$111.40
7 purchase totals =	$705.41		$772.8503	$772.85	$772.90	$772.80