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	$70.93	10.733%	$78.5429	$78.54	$78.55	$78.50
Purchase #2	$162.77	11.759%	$181.9101	$181.91	$181.90	$181.90
Purchase #3	$182.96	4.591%	$191.3597	$191.36	$191.35	$191.40
Purchase #4	$152.29	13.174%	$172.3527	$172.35	$172.35	$172.40
Purchase #5	$223.77	5.419%	$235.8961	$235.90	$235.90	$235.90
Purchase #6	$59.66	9.438%	$65.2907	$65.29	$65.30	$65.30
Purchase #7	$20.82	11.455%	$23.2049	$23.20	$23.20	$23.20
7 purchase totals =	$873.20		$948.5571	$948.55	$948.55	$948.60