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	$117.26	9.521%	$128.4243	$128.42	$128.40	$128.40
Purchase #2	$159.59	13.502%	$181.1378	$181.14	$181.15	$181.10
Purchase #3	$152.71	9.696%	$167.5168	$167.52	$167.50	$167.50
Purchase #4	$118.62	5.699%	$125.3802	$125.38	$125.40	$125.40
Purchase #5	$213.91	9.356%	$233.9234	$233.92	$233.90	$233.90
Purchase #6	$147.85	13.341%	$167.5747	$167.57	$167.55	$167.60
Purchase #7	$12.79	10.550%	$14.1393	$14.14	$14.15	$14.10
7 purchase totals =	$922.73		$1,018.0965	$1,018.09	$1,018.05	$1,018.00