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	$211.86	4.644%	$221.6988	$221.70	$221.70	$221.70
Purchase #2	$88.34	13.770%	$100.5044	$100.50	$100.50	$100.50
Purchase #3	$123.97	12.366%	$139.3001	$139.30	$139.30	$139.30
Purchase #4	$18.73	9.415%	$20.4934	$20.49	$20.50	$20.50
Purchase #5	$42.92	9.381%	$46.9463	$46.95	$46.95	$46.90
Purchase #6	$85.98	5.601%	$90.7957	$90.80	$90.80	$90.80
Purchase #7	$135.53	11.794%	$151.5144	$151.51	$151.50	$151.50
7 purchase totals =	$707.33		$771.2531	$771.25	$771.25	$771.20