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	$226.35	3.296%	$233.8105	$233.81	$233.80	$233.80
Purchase #2	$207.62	11.316%	$231.1143	$231.11	$231.10	$231.10
Purchase #3	$110.34	12.814%	$124.479	$124.48	$124.50	$124.50
Purchase #4	$80.48	12.274%	$90.3581	$90.36	$90.35	$90.40
Purchase #5	$177.47	10.820%	$196.6723	$196.67	$196.65	$196.70
Purchase #6	$221.68	7.643%	$238.623	$238.62	$238.60	$238.60
Purchase #7	$221.31	4.483%	$231.2313	$231.23	$231.25	$231.20
7 purchase totals =	$1,245.25		$1,346.2885	$1,346.28	$1,346.25	$1,346.30