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	$186.96	4.354%	$195.1002	$195.10	$195.10	$195.10
Purchase #2	$156.89	9.522%	$171.8291	$171.83	$171.85	$171.80
Purchase #3	$173.27	10.517%	$191.4928	$191.49	$191.50	$191.50
Purchase #4	$181.40	4.834%	$190.1689	$190.17	$190.15	$190.20
Purchase #5	$199.72	11.166%	$222.0207	$222.02	$222.00	$222.00
Purchase #6	$44.70	12.625%	$50.3434	$50.34	$50.35	$50.30
Purchase #7	$198.88	8.662%	$216.107	$216.11	$216.10	$216.10
7 purchase totals =	$1,141.82		$1,237.0621	$1,237.06	$1,237.05	$1,237.00