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	$129.75	5.696%	$137.1406	$137.14	$137.15	$137.10
Purchase #2	$148.93	11.803%	$166.5082	$166.51	$166.50	$166.50
Purchase #3	$83.55	6.713%	$89.1587	$89.16	$89.15	$89.20
Purchase #4	$21.63	11.526%	$24.1231	$24.12	$24.10	$24.10
Purchase #5	$228.79	9.643%	$250.8522	$250.85	$250.85	$250.90
Purchase #6	$121.29	9.685%	$133.0369	$133.04	$133.05	$133.00
Purchase #7	$196.81	6.378%	$209.3625	$209.36	$209.35	$209.40
7 purchase totals =	$930.75		$1,010.1822	$1,010.18	$1,010.15	$1,010.20