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	$163.28	3.428%	$168.8772	$168.88	$168.90	$168.90
Purchase #2	$10.82	13.310%	$12.2601	$12.26	$12.25	$12.30
Purchase #3	$11.77	13.534%	$13.363	$13.36	$13.35	$13.40
Purchase #4	$204.77	10.122%	$225.4968	$225.50	$225.50	$225.50
Purchase #5	$40.91	6.318%	$43.4947	$43.49	$43.50	$43.50
Purchase #6	$238.69	10.240%	$263.1319	$263.13	$263.15	$263.10
Purchase #7	$59.79	5.210%	$62.9051	$62.91	$62.90	$62.90
7 purchase totals =	$730.03		$789.5288	$789.53	$789.55	$789.60