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	$213.89	6.823%	$228.4837	$228.48	$228.50	$228.50
Purchase #2	$124.41	13.530%	$141.2427	$141.24	$141.25	$141.20
Purchase #3	$218.44	8.627%	$237.2848	$237.28	$237.30	$237.30
Purchase #4	$153.99	9.794%	$169.0718	$169.07	$169.05	$169.10
Purchase #5	$42.73	6.492%	$45.504	$45.50	$45.50	$45.50
Purchase #6	$83.93	5.453%	$88.5067	$88.51	$88.50	$88.50
Purchase #7	$172.62	6.738%	$184.2511	$184.25	$184.25	$184.30
7 purchase totals =	$1,010.01		$1,094.3448	$1,094.33	$1,094.35	$1,094.40