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	$56.57	7.864%	$61.0187	$61.02	$61.00	$61.00
Purchase #2	$216.50	3.410%	$223.8827	$223.88	$223.90	$223.90
Purchase #3	$249.31	12.367%	$280.1422	$280.14	$280.15	$280.10
Purchase #4	$188.77	7.308%	$202.5653	$202.57	$202.55	$202.60
Purchase #5	$148.48	11.196%	$165.1038	$165.10	$165.10	$165.10
Purchase #6	$192.86	13.818%	$219.5094	$219.51	$219.50	$219.50
Purchase #7	$100.37	4.103%	$104.4882	$104.49	$104.50	$104.50
7 purchase totals =	$1,152.86		$1,256.7103	$1,256.71	$1,256.70	$1,256.70