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	$191.84	10.578%	$212.1328	$212.13	$212.15	$212.10
Purchase #2	$78.77	5.149%	$82.8259	$82.83	$82.85	$82.80
Purchase #3	$70.96	9.572%	$77.7523	$77.75	$77.75	$77.80
Purchase #4	$239.41	12.717%	$269.8558	$269.86	$269.85	$269.90
Purchase #5	$220.71	4.282%	$230.1608	$230.16	$230.15	$230.20
Purchase #6	$52.83	4.408%	$55.1587	$55.16	$55.15	$55.20
Purchase #7	$159.49	3.647%	$165.3066	$165.31	$165.30	$165.30
7 purchase totals =	$1,014.01		$1,093.1929	$1,093.20	$1,093.20	$1,093.30