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	$91.78	8.552%	$99.629	$99.63	$99.65	$99.60
Purchase #2	$31.55	6.145%	$33.4887	$33.49	$33.50	$33.50
Purchase #3	$150.70	7.829%	$162.4983	$162.50	$162.50	$162.50
Purchase #4	$149.67	13.506%	$169.8844	$169.88	$169.90	$169.90
Purchase #5	$146.95	12.803%	$165.764	$165.76	$165.75	$165.80
Purchase #6	$6.30	4.572%	$6.588	$6.59	$6.60	$6.60
Purchase #7	$78.85	5.360%	$83.0764	$83.08	$83.10	$83.10
7 purchase totals =	$655.80		$720.9288	$720.93	$721.00	$721.00