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	$80.36	3.705%	$83.3373	$83.34	$83.35	$83.30
Purchase #2	$121.95	7.175%	$130.6999	$130.70	$130.70	$130.70
Purchase #3	$244.27	3.293%	$252.3138	$252.31	$252.30	$252.30
Purchase #4	$66.44	8.282%	$71.9426	$71.94	$71.95	$71.90
Purchase #5	$68.56	5.485%	$72.3205	$72.32	$72.30	$72.30
Purchase #6	$233.60	12.352%	$262.4543	$262.45	$262.45	$262.50
Purchase #7	$232.47	7.786%	$250.5701	$250.57	$250.55	$250.60
7 purchase totals =	$1,047.65		$1,123.6385	$1,123.63	$1,123.60	$1,123.60