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	$62.99	11.831%	$70.4423	$70.44	$70.45	$70.40
Purchase #2	$163.56	10.839%	$181.2883	$181.29	$181.30	$181.30
Purchase #3	$132.29	11.300%	$147.2388	$147.24	$147.25	$147.20
Purchase #4	$242.90	3.287%	$250.8841	$250.88	$250.90	$250.90
Purchase #5	$172.44	9.566%	$188.9356	$188.94	$188.95	$188.90
Purchase #6	$125.25	5.507%	$132.1475	$132.15	$132.15	$132.10
Purchase #7	$149.39	10.767%	$165.4748	$165.47	$165.45	$165.50
7 purchase totals =	$1,048.82		$1,136.4114	$1,136.41	$1,136.45	$1,136.30