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	$177.39	7.636%	$190.9355	$190.94	$190.95	$190.90
Purchase #2	$207.99	3.869%	$216.0371	$216.04	$216.05	$216.00
Purchase #3	$72.40	13.301%	$82.0299	$82.03	$82.05	$82.00
Purchase #4	$75.43	8.776%	$82.0497	$82.05	$82.05	$82.00
Purchase #5	$222.58	8.669%	$241.8755	$241.88	$241.90	$241.90
Purchase #6	$213.46	6.772%	$227.9155	$227.92	$227.90	$227.90
Purchase #7	$55.96	12.130%	$62.7479	$62.75	$62.75	$62.70
7 purchase totals =	$1,025.21		$1,103.5911	$1,103.61	$1,103.65	$1,103.40