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	$45.29	10.729%	$50.1492	$50.15	$50.15	$50.10
Purchase #2	$33.34	12.744%	$37.5888	$37.59	$37.60	$37.60
Purchase #3	$146.94	5.525%	$155.0584	$155.06	$155.05	$155.10
Purchase #4	$39.95	7.790%	$43.0621	$43.06	$43.05	$43.10
Purchase #5	$212.31	7.732%	$228.7258	$228.73	$228.75	$228.70
Purchase #6	$238.31	12.496%	$268.0892	$268.09	$268.10	$268.10
Purchase #7	$224.31	11.588%	$250.303	$250.30	$250.30	$250.30
7 purchase totals =	$940.45		$1,032.9765	$1,032.98	$1,033.00	$1,033.00