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	$63.68	12.575%	$71.6878	$71.69	$71.70	$71.70
Purchase #2	$106.28	12.685%	$119.7616	$119.76	$119.75	$119.80
Purchase #3	$89.49	5.426%	$94.3457	$94.35	$94.35	$94.30
Purchase #4	$37.69	12.172%	$42.2776	$42.28	$42.30	$42.30
Purchase #5	$33.81	6.302%	$35.9407	$35.94	$35.95	$35.90
Purchase #6	$236.46	11.432%	$263.4921	$263.49	$263.50	$263.50
Purchase #7	$144.40	12.807%	$162.8933	$162.89	$162.90	$162.90
7 purchase totals =	$711.81		$790.3988	$790.40	$790.45	$790.40