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	$150.65	5.195%	$158.4763	$158.48	$158.50	$158.50
Purchase #2	$53.89	6.692%	$57.4963	$57.50	$57.50	$57.50
Purchase #3	$163.29	7.102%	$174.8869	$174.89	$174.90	$174.90
Purchase #4	$114.58	6.507%	$122.0357	$122.04	$122.05	$122.00
Purchase #5	$134.96	11.219%	$150.1012	$150.10	$150.10	$150.10
Purchase #6	$29.69	13.834%	$33.7973	$33.80	$33.80	$33.80
Purchase #7	$62.46	8.521%	$67.7822	$67.78	$67.80	$67.80
7 purchase totals =	$709.52		$764.5759	$764.59	$764.65	$764.60