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	$59.97	9.679%	$65.7745	$65.77	$65.75	$65.80
Purchase #2	$184.73	3.790%	$191.7313	$191.73	$191.75	$191.70
Purchase #3	$181.25	6.802%	$193.5786	$193.58	$193.60	$193.60
Purchase #4	$194.69	13.616%	$221.199	$221.20	$221.20	$221.20
Purchase #5	$178.50	10.233%	$196.7659	$196.77	$196.75	$196.80
Purchase #6	$41.53	3.396%	$42.9404	$42.94	$42.95	$42.90
Purchase #7	$29.76	13.195%	$33.6868	$33.69	$33.70	$33.70
7 purchase totals =	$870.43		$945.6765	$945.68	$945.70	$945.70