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	$138.82	5.243%	$146.0983	$146.10	$146.10	$146.10
Purchase #2	$182.58	6.874%	$195.1305	$195.13	$195.15	$195.10
Purchase #3	$131.69	10.214%	$145.1408	$145.14	$145.15	$145.10
Purchase #4	$61.57	3.707%	$63.8524	$63.85	$63.85	$63.90
Purchase #5	$77.86	5.707%	$82.3035	$82.30	$82.30	$82.30
Purchase #6	$107.49	5.418%	$113.3138	$113.31	$113.30	$113.30
Purchase #7	$53.99	3.502%	$55.8807	$55.88	$55.90	$55.90
7 purchase totals =	$754.00		$801.7200	$801.71	$801.75	$801.70