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	$191.66	12.139%	$214.9256	$214.93	$214.95	$214.90
Purchase #2	$158.58	5.580%	$167.4288	$167.43	$167.45	$167.40
Purchase #3	$148.36	5.660%	$156.7572	$156.76	$156.75	$156.80
Purchase #4	$77.64	6.656%	$82.8077	$82.81	$82.80	$82.80
Purchase #5	$43.89	4.498%	$45.8642	$45.86	$45.85	$45.90
Purchase #6	$75.84	4.647%	$79.3643	$79.36	$79.35	$79.40
Purchase #7	$53.40	13.107%	$60.3991	$60.40	$60.40	$60.40
7 purchase totals =	$749.37		$807.5469	$807.55	$807.55	$807.60