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	$60.45	10.794%	$66.975	$66.98	$67.00	$67.00
Purchase #2	$199.70	10.379%	$220.4269	$220.43	$220.45	$220.40
Purchase #3	$213.35	13.110%	$241.3202	$241.32	$241.30	$241.30
Purchase #4	$98.33	7.118%	$105.3291	$105.33	$105.35	$105.30
Purchase #5	$162.62	11.621%	$181.5181	$181.52	$181.50	$181.50
Purchase #6	$223.53	4.638%	$233.8973	$233.90	$233.90	$233.90
Purchase #7	$193.32	8.316%	$209.3965	$209.40	$209.40	$209.40
7 purchase totals =	$1,151.30		$1,258.8631	$1,258.88	$1,258.90	$1,258.80