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	$200.43	11.621%	$223.722	$223.72	$223.70	$223.70
Purchase #2	$219.89	4.549%	$229.8928	$229.89	$229.90	$229.90
Purchase #3	$77.47	8.397%	$83.9752	$83.98	$84.00	$84.00
Purchase #4	$184.97	7.181%	$198.2527	$198.25	$198.25	$198.30
Purchase #5	$167.71	10.354%	$185.0747	$185.07	$185.05	$185.10
Purchase #6	$162.75	11.724%	$181.8308	$181.83	$181.85	$181.80
Purchase #7	$85.48	3.378%	$88.3675	$88.37	$88.35	$88.40
7 purchase totals =	$1,098.70		$1,191.1157	$1,191.11	$1,191.10	$1,191.20