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	$55.79	11.790%	$62.3676	$62.37	$62.35	$62.40
Purchase #2	$232.80	12.213%	$261.2319	$261.23	$261.25	$261.20
Purchase #3	$219.66	10.231%	$242.1334	$242.13	$242.15	$242.10
Purchase #4	$56.49	9.552%	$61.8859	$61.89	$61.90	$61.90
Purchase #5	$6.70	9.256%	$7.3202	$7.32	$7.30	$7.30
Purchase #6	$82.30	8.266%	$89.1029	$89.10	$89.10	$89.10
Purchase #7	$165.42	4.730%	$173.2444	$173.24	$173.25	$173.20
7 purchase totals =	$819.16		$897.2863	$897.28	$897.30	$897.20