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	$248.42	7.759%	$267.6949	$267.69	$267.70	$267.70
Purchase #2	$46.86	11.867%	$52.4209	$52.42	$52.40	$52.40
Purchase #3	$113.32	10.767%	$125.5212	$125.52	$125.50	$125.50
Purchase #4	$115.56	4.132%	$120.3349	$120.33	$120.35	$120.30
Purchase #5	$241.85	13.244%	$273.8806	$273.88	$273.90	$273.90
Purchase #6	$151.64	5.414%	$159.8498	$159.85	$159.85	$159.80
Purchase #7	$180.28	11.303%	$200.657	$200.66	$200.65	$200.70
7 purchase totals =	$1,097.93		$1,200.3593	$1,200.35	$1,200.35	$1,200.30