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	$141.58	10.506%	$156.4544	$156.45	$156.45	$156.50
Purchase #2	$237.78	10.845%	$263.5672	$263.57	$263.55	$263.60
Purchase #3	$136.33	7.227%	$146.1826	$146.18	$146.20	$146.20
Purchase #4	$120.84	8.862%	$131.5488	$131.55	$131.55	$131.50
Purchase #5	$26.48	5.425%	$27.9165	$27.92	$27.90	$27.90
Purchase #6	$95.82	7.250%	$102.767	$102.77	$102.75	$102.80
Purchase #7	$167.49	3.364%	$173.1244	$173.12	$173.10	$173.10
7 purchase totals =	$926.32		$1,001.5609	$1,001.56	$1,001.50	$1,001.60