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	$118.76	10.527%	$131.2619	$131.26	$131.25	$131.30
Purchase #2	$115.91	7.576%	$124.6913	$124.69	$124.70	$124.70
Purchase #3	$142.60	6.276%	$151.5496	$151.55	$151.55	$151.50
Purchase #4	$169.58	4.759%	$177.6503	$177.65	$177.65	$177.70
Purchase #5	$54.50	9.675%	$59.7729	$59.77	$59.75	$59.80
Purchase #6	$136.82	11.628%	$152.7294	$152.73	$152.75	$152.70
Purchase #7	$243.93	12.230%	$273.7626	$273.76	$273.75	$273.80
7 purchase totals =	$982.10		$1,071.4180	$1,071.41	$1,071.40	$1,071.50