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	$56.69	8.593%	$61.5614	$61.56	$61.55	$61.60
Purchase #2	$61.67	6.662%	$65.7785	$65.78	$65.80	$65.80
Purchase #3	$149.86	6.696%	$159.8946	$159.89	$159.90	$159.90
Purchase #4	$50.45	5.406%	$53.1773	$53.18	$53.20	$53.20
Purchase #5	$39.33	5.691%	$41.5683	$41.57	$41.55	$41.60
Purchase #6	$109.67	3.365%	$113.3604	$113.36	$113.35	$113.40
Purchase #7	$29.88	4.748%	$31.2987	$31.30	$31.30	$31.30
7 purchase totals =	$497.55		$526.6392	$526.64	$526.65	$526.80