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	$87.51	9.144%	$95.5119	$95.51	$95.50	$95.50
Purchase #2	$161.62	4.343%	$168.6392	$168.64	$168.65	$168.60
Purchase #3	$188.89	3.866%	$196.1925	$196.19	$196.20	$196.20
Purchase #4	$173.60	8.224%	$187.8769	$187.88	$187.90	$187.90
Purchase #5	$61.86	9.558%	$67.7726	$67.77	$67.75	$67.80
Purchase #6	$217.77	10.637%	$240.9342	$240.93	$240.95	$240.90
Purchase #7	$170.90	10.661%	$189.1196	$189.12	$189.10	$189.10
7 purchase totals =	$1,062.15		$1,146.0469	$1,146.04	$1,146.05	$1,146.00