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	$133.55	11.494%	$148.9002	$148.90	$148.90	$148.90
Purchase #2	$158.71	13.161%	$179.5978	$179.60	$179.60	$179.60
Purchase #3	$70.27	4.805%	$73.6465	$73.65	$73.65	$73.60
Purchase #4	$95.54	3.184%	$98.582	$98.58	$98.60	$98.60
Purchase #5	$248.65	8.707%	$270.3	$270.30	$270.30	$270.30
Purchase #6	$112.30	3.658%	$116.4079	$116.41	$116.40	$116.40
Purchase #7	$79.76	12.218%	$89.5051	$89.51	$89.50	$89.50
7 purchase totals =	$898.78		$976.9395	$976.95	$976.95	$976.90