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	$156.59	11.726%	$174.9517	$174.95	$174.95	$175.00
Purchase #2	$99.71	12.794%	$112.4669	$112.47	$112.45	$112.50
Purchase #3	$74.55	8.182%	$80.6497	$80.65	$80.65	$80.60
Purchase #4	$88.98	5.821%	$94.1595	$94.16	$94.15	$94.20
Purchase #5	$101.38	3.216%	$104.6404	$104.64	$104.65	$104.60
Purchase #6	$181.47	13.796%	$206.5056	$206.51	$206.50	$206.50
Purchase #7	$206.48	11.181%	$229.5665	$229.57	$229.55	$229.60
7 purchase totals =	$909.16		$1,002.9403	$1,002.95	$1,002.90	$1,003.00