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	$144.90	4.591%	$151.5524	$151.55	$151.55	$151.60
Purchase #2	$183.55	8.305%	$198.7938	$198.79	$198.80	$198.80
Purchase #3	$178.45	9.569%	$195.5259	$195.53	$195.55	$195.50
Purchase #4	$28.45	4.549%	$29.7442	$29.74	$29.75	$29.70
Purchase #5	$36.58	8.274%	$39.6066	$39.61	$39.60	$39.60
Purchase #6	$199.43	11.365%	$222.0952	$222.10	$222.10	$222.10
Purchase #7	$91.51	8.807%	$99.5693	$99.57	$99.55	$99.60
7 purchase totals =	$862.87		$936.8874	$936.89	$936.90	$936.90