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	$225.89	9.351%	$247.013	$247.01	$247.00	$247.00
Purchase #2	$132.46	5.833%	$140.1864	$140.19	$140.20	$140.20
Purchase #3	$242.80	3.251%	$250.6934	$250.69	$250.70	$250.70
Purchase #4	$18.56	10.685%	$20.5431	$20.54	$20.55	$20.50
Purchase #5	$51.66	7.565%	$55.5681	$55.57	$55.55	$55.60
Purchase #6	$109.89	9.747%	$120.601	$120.60	$120.60	$120.60
Purchase #7	$167.44	4.102%	$174.3084	$174.31	$174.30	$174.30
7 purchase totals =	$948.70		$1,008.9134	$1,008.91	$1,008.90	$1,008.90