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	$196.67	9.559%	$215.4697	$215.47	$215.45	$215.50
Purchase #2	$198.32	7.347%	$212.8906	$212.89	$212.90	$212.90
Purchase #3	$150.31	10.260%	$165.7318	$165.73	$165.75	$165.70
Purchase #4	$17.49	13.309%	$19.8177	$19.82	$19.80	$19.80
Purchase #5	$219.58	11.640%	$245.1391	$245.14	$245.15	$245.10
Purchase #6	$31.28	3.808%	$32.4711	$32.47	$32.45	$32.50
Purchase #7	$28.90	12.767%	$32.5897	$32.59	$32.60	$32.60
7 purchase totals =	$842.55		$924.1097	$924.11	$924.10	$924.10