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	$213.89	4.579%	$223.684	$223.68	$223.70	$223.70
Purchase #2	$147.45	8.752%	$160.3548	$160.35	$160.35	$160.40
Purchase #3	$93.43	6.715%	$99.7038	$99.70	$99.70	$99.70
Purchase #4	$169.91	12.497%	$191.1437	$191.14	$191.15	$191.10
Purchase #5	$84.30	5.595%	$89.0166	$89.02	$89.00	$89.00
Purchase #6	$199.68	9.233%	$218.1165	$218.12	$218.10	$218.10
Purchase #7	$60.48	6.447%	$64.3791	$64.38	$64.40	$64.40
7 purchase totals =	$969.14		$1,046.3985	$1,046.39	$1,046.40	$1,046.40