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	$148.76	12.277%	$167.0233	$167.02	$167.00	$167.00
Purchase #2	$190.61	5.121%	$200.3711	$200.37	$200.35	$200.40
Purchase #3	$28.88	12.533%	$32.4995	$32.50	$32.50	$32.50
Purchase #4	$30.55	7.864%	$32.9525	$32.95	$32.95	$33.00
Purchase #5	$62.45	3.348%	$64.5408	$64.54	$64.55	$64.50
Purchase #6	$226.95	9.631%	$248.8076	$248.81	$248.80	$248.80
Purchase #7	$146.30	8.254%	$158.3756	$158.38	$158.40	$158.40
7 purchase totals =	$834.50		$904.5704	$904.57	$904.55	$904.60