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	$143.79	5.527%	$151.7373	$151.74	$151.75	$151.70
Purchase #2	$82.98	7.810%	$89.4607	$89.46	$89.45	$89.50
Purchase #3	$30.35	11.603%	$33.8715	$33.87	$33.85	$33.90
Purchase #4	$243.77	8.149%	$263.6348	$263.63	$263.65	$263.60
Purchase #5	$166.74	13.620%	$189.45	$189.45	$189.45	$189.50
Purchase #6	$182.31	5.459%	$192.2623	$192.26	$192.25	$192.30
Purchase #7	$148.35	13.567%	$168.4766	$168.48	$168.50	$168.50
7 purchase totals =	$998.29		$1,088.8932	$1,088.89	$1,088.90	$1,089.00