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	$125.67	8.854%	$136.7968	$136.80	$136.80	$136.80
Purchase #2	$142.56	6.459%	$151.768	$151.77	$151.75	$151.80
Purchase #3	$141.86	3.579%	$146.9372	$146.94	$146.95	$146.90
Purchase #4	$241.30	11.120%	$268.1326	$268.13	$268.15	$268.10
Purchase #5	$68.93	3.190%	$71.1289	$71.13	$71.15	$71.10
Purchase #6	$18.59	10.640%	$20.568	$20.57	$20.55	$20.60
Purchase #7	$246.83	10.268%	$272.1745	$272.17	$272.15	$272.20
7 purchase totals =	$985.74		$1,067.5060	$1,067.51	$1,067.50	$1,067.50