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	$42.83	3.793%	$44.4545	$44.45	$44.45	$44.50
Purchase #2	$76.39	13.760%	$86.9013	$86.90	$86.90	$86.90
Purchase #3	$39.83	5.301%	$41.9414	$41.94	$41.95	$41.90
Purchase #4	$31.33	10.715%	$34.687	$34.69	$34.70	$34.70
Purchase #5	$87.53	4.300%	$91.2938	$91.29	$91.30	$91.30
Purchase #6	$110.29	7.374%	$118.4228	$118.42	$118.40	$118.40
Purchase #7	$186.80	13.216%	$211.4875	$211.49	$211.50	$211.50
7 purchase totals =	$575.00		$629.1883	$629.18	$629.20	$629.20