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	$156.38	11.707%	$174.6874	$174.69	$174.70	$174.70
Purchase #2	$64.56	12.553%	$72.6642	$72.66	$72.65	$72.70
Purchase #3	$36.76	13.796%	$41.8314	$41.83	$41.85	$41.80
Purchase #4	$183.38	12.202%	$205.756	$205.76	$205.75	$205.80
Purchase #5	$125.82	4.656%	$131.6782	$131.68	$131.70	$131.70
Purchase #6	$79.41	12.602%	$89.4172	$89.42	$89.40	$89.40
Purchase #7	$108.44	6.612%	$115.6101	$115.61	$115.60	$115.60
7 purchase totals =	$754.75		$831.6445	$831.65	$831.65	$831.70