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	$212.86	10.774%	$235.7935	$235.79	$235.80	$235.80
Purchase #2	$215.38	13.443%	$244.3335	$244.33	$244.35	$244.30
Purchase #3	$192.30	11.653%	$214.7087	$214.71	$214.70	$214.70
Purchase #4	$79.82	11.712%	$89.1685	$89.17	$89.15	$89.20
Purchase #5	$29.85	10.469%	$32.975	$32.98	$33.00	$33.00
Purchase #6	$120.28	13.523%	$136.5455	$136.55	$136.55	$136.50
Purchase #7	$157.52	11.365%	$175.4221	$175.42	$175.40	$175.40
7 purchase totals =	$1,008.01		$1,128.9468	$1,128.95	$1,128.95	$1,128.90