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	$99.66	4.859%	$104.5025	$104.50	$104.50	$104.50
Purchase #2	$113.86	9.150%	$124.2782	$124.28	$124.30	$124.30
Purchase #3	$57.29	7.738%	$61.7231	$61.72	$61.70	$61.70
Purchase #4	$135.92	6.158%	$144.29	$144.29	$144.30	$144.30
Purchase #5	$31.51	5.405%	$33.2131	$33.21	$33.20	$33.20
Purchase #6	$81.74	7.190%	$87.6171	$87.62	$87.60	$87.60
Purchase #7	$169.47	6.142%	$179.8788	$179.88	$179.90	$179.90
7 purchase totals =	$689.45		$735.5028	$735.50	$735.50	$735.50