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	$168.70	12.333%	$189.5058	$189.51	$189.50	$189.50
Purchase #2	$116.35	6.115%	$123.4648	$123.46	$123.45	$123.50
Purchase #3	$32.25	9.455%	$35.2992	$35.30	$35.30	$35.30
Purchase #4	$67.28	7.160%	$72.0972	$72.10	$72.10	$72.10
Purchase #5	$93.50	13.526%	$106.1468	$106.15	$106.15	$106.10
Purchase #6	$7.76	7.277%	$8.3247	$8.32	$8.30	$8.30
Purchase #7	$220.31	4.415%	$230.0367	$230.04	$230.05	$230.00
7 purchase totals =	$706.15		$764.8752	$764.88	$764.85	$764.80