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	$110.72	5.864%	$117.2126	$117.21	$117.20	$117.20
Purchase #2	$83.85	8.363%	$90.8624	$90.86	$90.85	$90.90
Purchase #3	$179.31	5.790%	$189.692	$189.69	$189.70	$189.70
Purchase #4	$20.37	13.102%	$23.0389	$23.04	$23.05	$23.00
Purchase #5	$92.86	13.609%	$105.4973	$105.50	$105.50	$105.50
Purchase #6	$73.93	5.744%	$78.1765	$78.18	$78.20	$78.20
Purchase #7	$88.33	8.549%	$95.8813	$95.88	$95.90	$95.90
7 purchase totals =	$649.37		$700.3610	$700.36	$700.40	$700.40