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	$219.77	10.738%	$243.3689	$243.37	$243.35	$243.40
Purchase #2	$90.87	11.434%	$101.2601	$101.26	$101.25	$101.30
Purchase #3	$189.59	11.626%	$211.6317	$211.63	$211.65	$211.60
Purchase #4	$192.28	4.311%	$200.5692	$200.57	$200.55	$200.60
Purchase #5	$230.91	5.400%	$243.3791	$243.38	$243.40	$243.40
Purchase #6	$50.32	11.738%	$56.2266	$56.23	$56.25	$56.20
Purchase #7	$66.63	7.603%	$71.6959	$71.70	$71.70	$71.70
7 purchase totals =	$1,040.37		$1,128.1315	$1,128.14	$1,128.15	$1,128.20