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	$119.39	10.827%	$132.3164	$132.32	$132.30	$132.30
Purchase #2	$38.58	12.242%	$43.303	$43.30	$43.30	$43.30
Purchase #3	$237.96	3.261%	$245.7199	$245.72	$245.70	$245.70
Purchase #4	$48.25	3.774%	$50.071	$50.07	$50.05	$50.10
Purchase #5	$106.52	9.373%	$116.5041	$116.50	$116.50	$116.50
Purchase #6	$174.25	9.244%	$190.3577	$190.36	$190.35	$190.40
Purchase #7	$201.60	10.635%	$223.0402	$223.04	$223.05	$223.00
7 purchase totals =	$926.55		$1,001.3123	$1,001.31	$1,001.25	$1,001.30