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	$191.54	9.518%	$209.7708	$209.77	$209.75	$209.80
Purchase #2	$187.88	6.675%	$200.421	$200.42	$200.40	$200.40
Purchase #3	$160.36	11.554%	$178.888	$178.89	$178.90	$178.90
Purchase #4	$64.70	8.477%	$70.1846	$70.18	$70.20	$70.20
Purchase #5	$109.93	3.483%	$113.7589	$113.76	$113.75	$113.80
Purchase #6	$99.44	13.551%	$112.9151	$112.92	$112.90	$112.90
Purchase #7	$247.70	9.767%	$271.8929	$271.89	$271.90	$271.90
7 purchase totals =	$1,061.55		$1,157.8313	$1,157.83	$1,157.80	$1,157.90