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	$193.82	3.567%	$200.7336	$200.73	$200.75	$200.70
Purchase #2	$249.90	9.844%	$274.5002	$274.50	$274.50	$274.50
Purchase #3	$199.37	6.164%	$211.6592	$211.66	$211.65	$211.70
Purchase #4	$26.42	13.119%	$29.886	$29.89	$29.90	$29.90
Purchase #5	$216.79	3.285%	$223.9116	$223.91	$223.90	$223.90
Purchase #6	$105.70	11.474%	$117.828	$117.83	$117.85	$117.80
Purchase #7	$158.30	8.549%	$171.8331	$171.83	$171.85	$171.80
7 purchase totals =	$1,150.30		$1,230.3517	$1,230.35	$1,230.40	$1,230.30