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	$74.30	5.414%	$78.3226	$78.32	$78.30	$78.30
Purchase #2	$10.64	4.424%	$11.1107	$11.11	$11.10	$11.10
Purchase #3	$197.78	10.520%	$218.5865	$218.59	$218.60	$218.60
Purchase #4	$123.88	5.833%	$131.1059	$131.11	$131.10	$131.10
Purchase #5	$146.37	13.398%	$165.9807	$165.98	$166.00	$166.00
Purchase #6	$210.97	10.624%	$233.3835	$233.38	$233.40	$233.40
Purchase #7	$58.39	13.239%	$66.1203	$66.12	$66.10	$66.10
7 purchase totals =	$822.33		$904.6102	$904.61	$904.60	$904.60