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	$23.47	7.117%	$25.1404	$25.14	$25.15	$25.10
Purchase #2	$66.92	7.833%	$72.1618	$72.16	$72.15	$72.20
Purchase #3	$243.53	8.632%	$264.5515	$264.55	$264.55	$264.60
Purchase #4	$96.52	9.693%	$105.8757	$105.88	$105.90	$105.90
Purchase #5	$153.93	8.461%	$166.954	$166.95	$166.95	$167.00
Purchase #6	$67.60	8.663%	$73.4562	$73.46	$73.45	$73.50
Purchase #7	$59.34	8.661%	$64.4794	$64.48	$64.50	$64.50
7 purchase totals =	$711.31		$772.6190	$772.62	$772.65	$772.80