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	$246.26	9.389%	$269.3814	$269.38	$269.40	$269.40
Purchase #2	$120.98	7.457%	$130.0015	$130.00	$130.00	$130.00
Purchase #3	$119.53	6.323%	$127.0879	$127.09	$127.10	$127.10
Purchase #4	$168.54	11.695%	$188.2508	$188.25	$188.25	$188.30
Purchase #5	$60.61	9.607%	$66.4328	$66.43	$66.45	$66.40
Purchase #6	$214.72	3.795%	$222.8686	$222.87	$222.85	$222.90
Purchase #7	$89.61	8.185%	$96.9446	$96.94	$96.95	$96.90
7 purchase totals =	$1,020.25		$1,100.9676	$1,100.96	$1,101.00	$1,101.00