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	$116.82	9.428%	$127.8338	$127.83	$127.85	$127.80
Purchase #2	$31.86	4.568%	$33.3154	$33.32	$33.30	$33.30
Purchase #3	$197.70	3.283%	$204.1905	$204.19	$204.20	$204.20
Purchase #4	$43.26	3.206%	$44.6469	$44.65	$44.65	$44.60
Purchase #5	$70.65	8.776%	$76.8502	$76.85	$76.85	$76.90
Purchase #6	$236.52	13.673%	$268.8594	$268.86	$268.85	$268.90
Purchase #7	$31.56	7.308%	$33.8664	$33.87	$33.85	$33.90
7 purchase totals =	$728.37		$789.5626	$789.57	$789.55	$789.60