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	$88.83	6.753%	$94.8287	$94.83	$94.85	$94.80
Purchase #2	$64.38	12.860%	$72.6593	$72.66	$72.65	$72.70
Purchase #3	$180.31	12.680%	$203.1733	$203.17	$203.15	$203.20
Purchase #4	$242.47	9.106%	$264.5493	$264.55	$264.55	$264.50
Purchase #5	$133.42	10.584%	$147.5412	$147.54	$147.55	$147.50
Purchase #6	$133.82	10.412%	$147.7533	$147.75	$147.75	$147.80
Purchase #7	$43.93	5.652%	$46.4129	$46.41	$46.40	$46.40
7 purchase totals =	$887.16		$976.9180	$976.91	$976.90	$976.90