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	$61.91	12.260%	$69.5002	$69.50	$69.50	$69.50
Purchase #2	$240.89	5.357%	$253.7945	$253.79	$253.80	$253.80
Purchase #3	$85.86	3.600%	$88.951	$88.95	$88.95	$89.00
Purchase #4	$219.51	6.282%	$233.2996	$233.30	$233.30	$233.30
Purchase #5	$102.79	8.118%	$111.1345	$111.13	$111.15	$111.10
Purchase #6	$131.82	13.223%	$149.2506	$149.25	$149.25	$149.30
Purchase #7	$152.45	10.842%	$168.9786	$168.98	$169.00	$169.00
7 purchase totals =	$995.23		$1,074.9090	$1,074.90	$1,074.95	$1,075.00