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	$115.70	6.843%	$123.6174	$123.62	$123.60	$123.60
Purchase #2	$75.59	3.256%	$78.0512	$78.05	$78.05	$78.10
Purchase #3	$238.83	9.335%	$261.1248	$261.12	$261.10	$261.10
Purchase #4	$151.43	6.210%	$160.8338	$160.83	$160.85	$160.80
Purchase #5	$243.85	9.796%	$267.7375	$267.74	$267.75	$267.70
Purchase #6	$171.76	9.294%	$187.7234	$187.72	$187.70	$187.70
Purchase #7	$22.48	12.281%	$25.2408	$25.24	$25.25	$25.20
7 purchase totals =	$1,019.64		$1,104.3289	$1,104.32	$1,104.30	$1,104.20