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	$87.82	8.501%	$95.2856	$95.29	$95.30	$95.30
Purchase #2	$204.83	4.403%	$213.8487	$213.85	$213.85	$213.80
Purchase #3	$136.98	6.808%	$146.3056	$146.31	$146.30	$146.30
Purchase #4	$158.79	13.765%	$180.6474	$180.65	$180.65	$180.60
Purchase #5	$150.60	9.375%	$164.7188	$164.72	$164.70	$164.70
Purchase #6	$219.56	12.595%	$247.2136	$247.21	$247.20	$247.20
Purchase #7	$55.28	7.802%	$59.5929	$59.59	$59.60	$59.60
7 purchase totals =	$1,013.86		$1,107.6126	$1,107.62	$1,107.60	$1,107.50