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	$98.31	6.107%	$104.3138	$104.31	$104.30	$104.30
Purchase #2	$92.51	8.383%	$100.2651	$100.27	$100.25	$100.30
Purchase #3	$114.90	10.772%	$127.277	$127.28	$127.30	$127.30
Purchase #4	$80.88	3.312%	$83.5587	$83.56	$83.55	$83.60
Purchase #5	$31.87	7.593%	$34.2899	$34.29	$34.30	$34.30
Purchase #6	$137.47	4.281%	$143.3551	$143.36	$143.35	$143.40
Purchase #7	$107.65	9.551%	$117.9317	$117.93	$117.95	$117.90
7 purchase totals =	$663.59		$710.9913	$711.00	$711.00	$711.10