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	$118.40	6.658%	$126.2831	$126.28	$126.30	$126.30
Purchase #2	$167.98	13.476%	$190.617	$190.62	$190.60	$190.60
Purchase #3	$187.59	12.179%	$210.4366	$210.44	$210.45	$210.40
Purchase #4	$195.51	11.657%	$218.3006	$218.30	$218.30	$218.30
Purchase #5	$29.50	5.607%	$31.1541	$31.15	$31.15	$31.20
Purchase #6	$215.95	5.735%	$228.3347	$228.33	$228.35	$228.30
Purchase #7	$41.62	8.840%	$45.2992	$45.30	$45.30	$45.30
7 purchase totals =	$956.55		$1,050.4253	$1,050.42	$1,050.45	$1,050.40