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	$89.47	12.668%	$100.8041	$100.80	$100.80	$100.80
Purchase #2	$204.29	3.828%	$212.1102	$212.11	$212.10	$212.10
Purchase #3	$167.37	8.210%	$181.1111	$181.11	$181.10	$181.10
Purchase #4	$138.36	11.224%	$153.8895	$153.89	$153.90	$153.90
Purchase #5	$171.52	3.109%	$176.8526	$176.85	$176.85	$176.90
Purchase #6	$88.60	13.802%	$100.8286	$100.83	$100.85	$100.80
Purchase #7	$96.42	3.422%	$99.7195	$99.72	$99.70	$99.70
7 purchase totals =	$956.03		$1,025.3156	$1,025.31	$1,025.30	$1,025.30