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	$121.48	7.352%	$130.4112	$130.41	$130.40	$130.40
Purchase #2	$217.41	5.231%	$228.7827	$228.78	$228.80	$228.80
Purchase #3	$69.43	11.348%	$77.3089	$77.31	$77.30	$77.30
Purchase #4	$64.82	8.448%	$70.296	$70.30	$70.30	$70.30
Purchase #5	$46.73	11.232%	$51.9787	$51.98	$52.00	$52.00
Purchase #6	$25.33	13.758%	$28.8149	$28.81	$28.80	$28.80
Purchase #7	$99.49	12.516%	$111.9422	$111.94	$111.95	$111.90
7 purchase totals =	$644.69		$699.5346	$699.53	$699.55	$699.50