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	$41.83	8.301%	$45.3023	$45.30	$45.30	$45.30
Purchase #2	$163.83	13.793%	$186.4271	$186.43	$186.45	$186.40
Purchase #3	$178.97	11.466%	$199.4907	$199.49	$199.50	$199.50
Purchase #4	$83.85	9.681%	$91.9675	$91.97	$91.95	$92.00
Purchase #5	$53.79	13.327%	$60.9586	$60.96	$60.95	$61.00
Purchase #6	$243.73	7.319%	$261.5686	$261.57	$261.55	$261.60
Purchase #7	$191.95	12.458%	$215.8631	$215.86	$215.85	$215.90
7 purchase totals =	$957.95		$1,061.5779	$1,061.58	$1,061.55	$1,061.70