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	$218.26	13.539%	$247.8102	$247.81	$247.80	$247.80
Purchase #2	$141.52	6.621%	$150.89	$150.89	$150.90	$150.90
Purchase #3	$92.31	11.632%	$103.0475	$103.05	$103.05	$103.00
Purchase #4	$80.95	3.328%	$83.644	$83.64	$83.65	$83.60
Purchase #5	$156.63	11.702%	$174.9588	$174.96	$174.95	$175.00
Purchase #6	$73.69	7.564%	$79.2639	$79.26	$79.25	$79.30
Purchase #7	$222.47	3.523%	$230.3076	$230.31	$230.30	$230.30
7 purchase totals =	$985.83		$1,069.9220	$1,069.92	$1,069.90	$1,069.90