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	$111.80	11.192%	$124.3127	$124.31	$124.30	$124.30
Purchase #2	$224.86	11.390%	$250.4716	$250.47	$250.45	$250.50
Purchase #3	$15.55	6.209%	$16.5155	$16.52	$16.50	$16.50
Purchase #4	$166.84	3.586%	$172.8229	$172.82	$172.80	$172.80
Purchase #5	$213.70	13.369%	$242.2696	$242.27	$242.25	$242.30
Purchase #6	$149.37	13.384%	$169.3617	$169.36	$169.35	$169.40
Purchase #7	$142.89	3.822%	$148.3513	$148.35	$148.35	$148.40
7 purchase totals =	$1,025.01		$1,124.1053	$1,124.10	$1,124.00	$1,124.20