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	$237.47	5.589%	$250.7422	$250.74	$250.75	$250.70
Purchase #2	$191.90	6.538%	$204.4464	$204.45	$204.45	$204.40
Purchase #3	$192.36	4.118%	$200.2814	$200.28	$200.30	$200.30
Purchase #4	$137.38	13.551%	$155.9964	$156.00	$156.00	$156.00
Purchase #5	$45.48	3.500%	$47.0718	$47.07	$47.05	$47.10
Purchase #6	$35.88	5.637%	$37.9026	$37.90	$37.90	$37.90
Purchase #7	$161.90	11.509%	$180.5331	$180.53	$180.55	$180.50
7 purchase totals =	$1,002.37		$1,076.9739	$1,076.97	$1,077.00	$1,076.90