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	$38.47	5.655%	$40.6455	$40.65	$40.65	$40.60
Purchase #2	$73.45	12.731%	$82.8009	$82.80	$82.80	$82.80
Purchase #3	$131.82	9.620%	$144.5011	$144.50	$144.50	$144.50
Purchase #4	$87.60	10.165%	$96.5045	$96.50	$96.50	$96.50
Purchase #5	$99.25	3.522%	$102.7456	$102.75	$102.75	$102.70
Purchase #6	$35.45	5.872%	$37.5316	$37.53	$37.55	$37.50
Purchase #7	$221.45	11.864%	$247.7228	$247.72	$247.70	$247.70
7 purchase totals =	$687.49		$752.4520	$752.45	$752.45	$752.30