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	$224.58	8.595%	$243.8827	$243.88	$243.90	$243.90
Purchase #2	$165.94	4.445%	$173.316	$173.32	$173.30	$173.30
Purchase #3	$165.26	5.791%	$174.8302	$174.83	$174.85	$174.80
Purchase #4	$98.85	7.421%	$106.1857	$106.19	$106.20	$106.20
Purchase #5	$83.71	7.835%	$90.2687	$90.27	$90.25	$90.30
Purchase #6	$48.64	7.246%	$52.1645	$52.16	$52.15	$52.20
Purchase #7	$231.65	11.144%	$257.4651	$257.47	$257.45	$257.50
7 purchase totals =	$1,018.63		$1,098.1129	$1,098.12	$1,098.10	$1,098.20