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	$34.61	7.849%	$37.3265	$37.33	$37.35	$37.30
Purchase #2	$30.63	5.364%	$32.273	$32.27	$32.25	$32.30
Purchase #3	$122.25	6.307%	$129.9603	$129.96	$129.95	$130.00
Purchase #4	$93.67	11.834%	$104.7549	$104.75	$104.75	$104.80
Purchase #5	$25.43	12.221%	$28.5378	$28.54	$28.55	$28.50
Purchase #6	$22.88	9.455%	$25.0433	$25.04	$25.05	$25.00
Purchase #7	$81.86	10.168%	$90.1835	$90.18	$90.20	$90.20
7 purchase totals =	$411.33		$448.0793	$448.07	$448.10	$448.10