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	$143.40	6.151%	$152.2205	$152.22	$152.20	$152.20
Purchase #2	$175.96	7.395%	$188.9722	$188.97	$188.95	$189.00
Purchase #3	$247.48	12.390%	$278.1428	$278.14	$278.15	$278.10
Purchase #4	$99.73	5.815%	$105.5293	$105.53	$105.55	$105.50
Purchase #5	$42.31	6.696%	$45.1431	$45.14	$45.15	$45.10
Purchase #6	$70.54	13.314%	$79.9317	$79.93	$79.95	$79.90
Purchase #7	$145.40	10.792%	$161.0916	$161.09	$161.10	$161.10
7 purchase totals =	$924.82		$1,011.0312	$1,011.02	$1,011.05	$1,010.90