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	$192.50	3.119%	$198.5041	$198.50	$198.50	$198.50
Purchase #2	$35.55	6.293%	$37.7872	$37.79	$37.80	$37.80
Purchase #3	$103.32	10.139%	$113.7956	$113.80	$113.80	$113.80
Purchase #4	$160.80	6.580%	$171.3806	$171.38	$171.40	$171.40
Purchase #5	$200.38	6.132%	$212.6673	$212.67	$212.65	$212.70
Purchase #6	$108.54	8.756%	$118.0438	$118.04	$118.05	$118.00
Purchase #7	$62.60	13.631%	$71.133	$71.13	$71.15	$71.10
7 purchase totals =	$863.69		$923.3116	$923.31	$923.35	$923.30