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	$92.41	4.539%	$96.6045	$96.60	$96.60	$96.60
Purchase #2	$76.61	4.632%	$80.1586	$80.16	$80.15	$80.20
Purchase #3	$215.83	9.426%	$236.1741	$236.17	$236.15	$236.20
Purchase #4	$179.69	11.523%	$200.3957	$200.40	$200.40	$200.40
Purchase #5	$244.55	8.211%	$264.63	$264.63	$264.65	$264.60
Purchase #6	$56.25	9.720%	$61.7175	$61.72	$61.70	$61.70
Purchase #7	$226.61	9.208%	$247.4762	$247.48	$247.50	$247.50
7 purchase totals =	$1,091.95		$1,187.1566	$1,187.16	$1,187.15	$1,187.20