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	$147.49	3.240%	$152.2687	$152.27	$152.25	$152.30
Purchase #2	$242.51	9.199%	$264.8185	$264.82	$264.80	$264.80
Purchase #3	$58.68	10.501%	$64.842	$64.84	$64.85	$64.80
Purchase #4	$36.76	5.446%	$38.7619	$38.76	$38.75	$38.80
Purchase #5	$241.92	9.860%	$265.7733	$265.77	$265.75	$265.80
Purchase #6	$243.82	10.348%	$269.0505	$269.05	$269.05	$269.10
Purchase #7	$14.71	11.716%	$16.4334	$16.43	$16.45	$16.40
7 purchase totals =	$985.89		$1,071.9483	$1,071.94	$1,071.90	$1,072.00