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	$148.33	7.560%	$159.5437	$159.54	$159.55	$159.50
Purchase #2	$69.42	10.383%	$76.6279	$76.63	$76.65	$76.60
Purchase #3	$147.96	4.402%	$154.4732	$154.47	$154.45	$154.50
Purchase #4	$57.91	3.489%	$59.9305	$59.93	$59.95	$59.90
Purchase #5	$179.72	10.174%	$198.0047	$198.00	$198.00	$198.00
Purchase #6	$112.29	13.487%	$127.4346	$127.43	$127.45	$127.40
Purchase #7	$99.75	5.181%	$104.918	$104.92	$104.90	$104.90
7 purchase totals =	$815.38		$880.9326	$880.92	$880.95	$880.80