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	$242.29	13.507%	$275.0161	$275.02	$275.00	$275.00
Purchase #2	$39.86	4.353%	$41.5951	$41.60	$41.60	$41.60
Purchase #3	$141.97	13.135%	$160.6178	$160.62	$160.60	$160.60
Purchase #4	$154.33	6.399%	$164.2056	$164.21	$164.20	$164.20
Purchase #5	$129.66	12.175%	$145.4461	$145.45	$145.45	$145.40
Purchase #6	$141.53	13.522%	$160.6677	$160.67	$160.65	$160.70
Purchase #7	$73.48	6.268%	$78.0857	$78.09	$78.10	$78.10
7 purchase totals =	$923.12		$1,025.6341	$1,025.66	$1,025.60	$1,025.60