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	$119.72	4.194%	$124.7411	$124.74	$124.75	$124.70
Purchase #2	$19.45	10.273%	$21.4481	$21.45	$21.45	$21.40
Purchase #3	$243.87	8.374%	$264.2917	$264.29	$264.30	$264.30
Purchase #4	$102.91	8.480%	$111.6368	$111.64	$111.65	$111.60
Purchase #5	$37.87	12.137%	$42.4663	$42.47	$42.45	$42.50
Purchase #6	$145.79	11.601%	$162.7031	$162.70	$162.70	$162.70
Purchase #7	$110.97	13.634%	$126.0996	$126.10	$126.10	$126.10
7 purchase totals =	$780.58		$853.3867	$853.39	$853.40	$853.30