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	$169.69	6.503%	$180.7249	$180.72	$180.70	$180.70
Purchase #2	$195.38	5.279%	$205.6941	$205.69	$205.70	$205.70
Purchase #3	$171.69	7.489%	$184.5479	$184.55	$184.55	$184.50
Purchase #4	$28.69	12.457%	$32.2639	$32.26	$32.25	$32.30
Purchase #5	$111.38	6.575%	$118.7032	$118.70	$118.70	$118.70
Purchase #6	$103.28	9.267%	$112.851	$112.85	$112.85	$112.90
Purchase #7	$55.95	11.244%	$62.241	$62.24	$62.25	$62.20
7 purchase totals =	$836.06		$897.0260	$897.01	$897.00	$897.00