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	$81.35	6.422%	$86.5743	$86.57	$86.55	$86.60
Purchase #2	$24.76	5.192%	$26.0455	$26.05	$26.05	$26.00
Purchase #3	$133.73	11.326%	$148.8763	$148.88	$148.90	$148.90
Purchase #4	$155.31	6.585%	$165.5372	$165.54	$165.55	$165.50
Purchase #5	$43.85	5.226%	$46.1416	$46.14	$46.15	$46.10
Purchase #6	$196.90	10.179%	$216.9425	$216.94	$216.95	$216.90
Purchase #7	$67.58	4.354%	$70.5224	$70.52	$70.50	$70.50
7 purchase totals =	$703.48		$760.6398	$760.64	$760.65	$760.50