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	$133.72	9.270%	$146.1158	$146.12	$146.10	$146.10
Purchase #2	$164.69	6.535%	$175.4525	$175.45	$175.45	$175.50
Purchase #3	$213.89	6.407%	$227.5939	$227.59	$227.60	$227.60
Purchase #4	$95.80	5.314%	$100.8908	$100.89	$100.90	$100.90
Purchase #5	$189.81	4.217%	$197.8143	$197.81	$197.80	$197.80
Purchase #6	$57.41	8.191%	$62.1125	$62.11	$62.10	$62.10
Purchase #7	$156.28	9.765%	$171.5407	$171.54	$171.55	$171.50
7 purchase totals =	$1,011.60		$1,081.5205	$1,081.51	$1,081.50	$1,081.50