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	$182.67	7.693%	$196.7228	$196.72	$196.70	$196.70
Purchase #2	$186.54	12.603%	$210.0496	$210.05	$210.05	$210.00
Purchase #3	$36.49	10.692%	$40.3915	$40.39	$40.40	$40.40
Purchase #4	$184.60	7.463%	$198.3767	$198.38	$198.40	$198.40
Purchase #5	$51.30	3.538%	$53.115	$53.12	$53.10	$53.10
Purchase #6	$97.51	8.525%	$105.8227	$105.82	$105.80	$105.80
Purchase #7	$149.26	4.322%	$155.711	$155.71	$155.70	$155.70
7 purchase totals =	$888.37		$960.1893	$960.19	$960.15	$960.10