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	$115.92	13.734%	$131.8405	$131.84	$131.85	$131.80
Purchase #2	$233.44	9.654%	$255.9763	$255.98	$256.00	$256.00
Purchase #3	$249.79	5.366%	$263.1937	$263.19	$263.20	$263.20
Purchase #4	$50.74	5.748%	$53.6565	$53.66	$53.65	$53.70
Purchase #5	$132.81	7.136%	$142.2873	$142.29	$142.30	$142.30
Purchase #6	$59.57	8.232%	$64.4738	$64.47	$64.45	$64.50
Purchase #7	$130.46	6.627%	$139.1056	$139.11	$139.10	$139.10
7 purchase totals =	$972.73		$1,050.5337	$1,050.54	$1,050.55	$1,050.60