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	$207.89	6.543%	$221.4922	$221.49	$221.50	$221.50
Purchase #2	$58.94	6.494%	$62.7676	$62.77	$62.75	$62.80
Purchase #3	$82.61	8.567%	$89.6872	$89.69	$89.70	$89.70
Purchase #4	$218.84	10.399%	$241.5972	$241.60	$241.60	$241.60
Purchase #5	$6.90	4.721%	$7.2257	$7.23	$7.25	$7.20
Purchase #6	$161.41	13.337%	$182.9373	$182.94	$182.95	$182.90
Purchase #7	$217.27	9.559%	$238.0388	$238.04	$238.05	$238.00
7 purchase totals =	$953.86		$1,043.7460	$1,043.76	$1,043.80	$1,043.70