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	$137.48	12.226%	$154.2883	$154.29	$154.30	$154.30
Purchase #2	$234.42	12.327%	$263.317	$263.32	$263.30	$263.30
Purchase #3	$112.86	10.152%	$124.3175	$124.32	$124.30	$124.30
Purchase #4	$6.70	11.851%	$7.494	$7.49	$7.50	$7.50
Purchase #5	$34.41	12.313%	$38.6469	$38.65	$38.65	$38.60
Purchase #6	$215.60	12.616%	$242.8001	$242.80	$242.80	$242.80
Purchase #7	$165.55	12.184%	$185.7206	$185.72	$185.70	$185.70
7 purchase totals =	$907.02		$1,016.5844	$1,016.59	$1,016.55	$1,016.50