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	$239.52	5.146%	$251.8457	$251.85	$251.85	$251.80
Purchase #2	$200.48	8.747%	$218.016	$218.02	$218.00	$218.00
Purchase #3	$232.83	8.355%	$252.2829	$252.28	$252.30	$252.30
Purchase #4	$160.89	12.278%	$180.6441	$180.64	$180.65	$180.60
Purchase #5	$46.64	13.399%	$52.8893	$52.89	$52.90	$52.90
Purchase #6	$37.84	6.607%	$40.3401	$40.34	$40.35	$40.30
Purchase #7	$42.88	6.110%	$45.5	$45.50	$45.50	$45.50
7 purchase totals =	$961.08		$1,041.5181	$1,041.52	$1,041.55	$1,041.40