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	$242.62	3.382%	$250.8254	$250.83	$250.85	$250.80
Purchase #2	$21.38	4.112%	$22.2591	$22.26	$22.25	$22.30
Purchase #3	$127.96	6.645%	$136.4629	$136.46	$136.45	$136.50
Purchase #4	$206.88	7.465%	$222.3236	$222.32	$222.30	$222.30
Purchase #5	$250.42	3.257%	$258.5762	$258.58	$258.60	$258.60
Purchase #6	$95.84	4.111%	$99.78	$99.78	$99.80	$99.80
Purchase #7	$120.95	8.699%	$131.4714	$131.47	$131.45	$131.50
7 purchase totals =	$1,066.05		$1,121.6986	$1,121.70	$1,121.70	$1,121.80