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	$32.71	10.395%	$36.1102	$36.11	$36.10	$36.10
Purchase #2	$134.48	7.435%	$144.4786	$144.48	$144.50	$144.50
Purchase #3	$110.91	7.459%	$119.1828	$119.18	$119.20	$119.20
Purchase #4	$143.98	6.760%	$153.713	$153.71	$153.70	$153.70
Purchase #5	$130.85	9.399%	$143.1486	$143.15	$143.15	$143.10
Purchase #6	$55.41	4.448%	$57.8746	$57.87	$57.85	$57.90
Purchase #7	$65.95	9.243%	$72.0458	$72.05	$72.05	$72.00
7 purchase totals =	$674.29		$726.5536	$726.55	$726.55	$726.50