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	$228.48	7.109%	$244.7226	$244.72	$244.70	$244.70
Purchase #2	$52.87	12.389%	$59.4201	$59.42	$59.40	$59.40
Purchase #3	$38.66	13.185%	$43.7573	$43.76	$43.75	$43.80
Purchase #4	$211.85	5.474%	$223.4467	$223.45	$223.45	$223.40
Purchase #5	$65.87	10.873%	$73.032	$73.03	$73.05	$73.00
Purchase #6	$150.36	5.202%	$158.1817	$158.18	$158.20	$158.20
Purchase #7	$96.95	10.244%	$106.8816	$106.88	$106.90	$106.90
7 purchase totals =	$845.04		$909.4420	$909.44	$909.45	$909.40