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	$186.43	8.454%	$202.1908	$202.19	$202.20	$202.20
Purchase #2	$106.83	5.345%	$112.5401	$112.54	$112.55	$112.50
Purchase #3	$157.92	8.654%	$171.5864	$171.59	$171.60	$171.60
Purchase #4	$243.87	12.839%	$275.1805	$275.18	$275.20	$275.20
Purchase #5	$245.25	7.855%	$264.5144	$264.51	$264.50	$264.50
Purchase #6	$144.92	5.500%	$152.8906	$152.89	$152.90	$152.90
Purchase #7	$245.40	4.207%	$255.724	$255.72	$255.70	$255.70
7 purchase totals =	$1,330.62		$1,434.6268	$1,434.62	$1,434.65	$1,434.60