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	$52.37	8.431%	$56.7853	$56.79	$56.80	$56.80
Purchase #2	$163.77	10.671%	$181.2459	$181.25	$181.25	$181.20
Purchase #3	$89.55	11.456%	$99.8088	$99.81	$99.80	$99.80
Purchase #4	$139.29	11.791%	$155.7137	$155.71	$155.70	$155.70
Purchase #5	$105.90	3.212%	$109.3015	$109.30	$109.30	$109.30
Purchase #6	$180.57	13.268%	$204.528	$204.53	$204.55	$204.50
Purchase #7	$230.31	12.503%	$259.1057	$259.11	$259.10	$259.10
7 purchase totals =	$961.76		$1,066.4889	$1,066.50	$1,066.50	$1,066.40