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	$104.31	7.598%	$112.2355	$112.24	$112.25	$112.20
Purchase #2	$131.50	13.581%	$149.359	$149.36	$149.35	$149.40
Purchase #3	$197.71	5.530%	$208.6434	$208.64	$208.65	$208.60
Purchase #4	$51.95	4.387%	$54.229	$54.23	$54.25	$54.20
Purchase #5	$196.79	13.200%	$222.7663	$222.77	$222.75	$222.80
Purchase #6	$72.98	6.736%	$77.8959	$77.90	$77.90	$77.90
Purchase #7	$246.40	9.687%	$270.2688	$270.27	$270.25	$270.30
7 purchase totals =	$1,001.64		$1,095.3979	$1,095.41	$1,095.40	$1,095.40