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	$217.98	10.592%	$241.0684	$241.07	$241.05	$241.10
Purchase #2	$83.66	6.577%	$89.1623	$89.16	$89.15	$89.20
Purchase #3	$160.48	4.254%	$167.3068	$167.31	$167.30	$167.30
Purchase #4	$140.77	11.751%	$157.3119	$157.31	$157.30	$157.30
Purchase #5	$147.98	11.689%	$165.2774	$165.28	$165.30	$165.30
Purchase #6	$82.77	11.252%	$92.0833	$92.08	$92.10	$92.10
Purchase #7	$52.70	8.109%	$56.9734	$56.97	$56.95	$57.00
7 purchase totals =	$886.34		$969.1835	$969.18	$969.15	$969.30