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	$113.60	8.508%	$123.2651	$123.27	$123.25	$123.30
Purchase #2	$120.71	5.355%	$127.174	$127.17	$127.15	$127.20
Purchase #3	$59.36	4.832%	$62.2283	$62.23	$62.25	$62.20
Purchase #4	$79.85	10.288%	$88.065	$88.07	$88.05	$88.10
Purchase #5	$159.94	10.130%	$176.1419	$176.14	$176.15	$176.10
Purchase #6	$90.90	10.278%	$100.2427	$100.24	$100.25	$100.20
Purchase #7	$196.77	12.114%	$220.6067	$220.61	$220.60	$220.60
7 purchase totals =	$821.13		$897.7237	$897.73	$897.70	$897.70