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	$92.43	4.411%	$96.5071	$96.51	$96.50	$96.50
Purchase #2	$248.52	10.683%	$275.0694	$275.07	$275.05	$275.10
Purchase #3	$176.40	9.156%	$192.5512	$192.55	$192.55	$192.60
Purchase #4	$47.68	12.406%	$53.5952	$53.60	$53.60	$53.60
Purchase #5	$85.72	12.589%	$96.5113	$96.51	$96.50	$96.50
Purchase #6	$237.28	11.518%	$264.6099	$264.61	$264.60	$264.60
Purchase #7	$97.76	12.206%	$109.6926	$109.69	$109.70	$109.70
7 purchase totals =	$985.79		$1,088.5367	$1,088.54	$1,088.50	$1,088.60