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	$223.75	6.611%	$238.5421	$238.54	$238.55	$238.50
Purchase #2	$90.40	9.103%	$98.6291	$98.63	$98.65	$98.60
Purchase #3	$136.25	3.611%	$141.17	$141.17	$141.15	$141.20
Purchase #4	$47.59	10.240%	$52.4632	$52.46	$52.45	$52.50
Purchase #5	$232.42	8.350%	$251.8271	$251.83	$251.85	$251.80
Purchase #6	$226.97	12.155%	$254.5582	$254.56	$254.55	$254.60
Purchase #7	$144.71	5.114%	$152.1105	$152.11	$152.10	$152.10
7 purchase totals =	$1,102.09		$1,189.3002	$1,189.30	$1,189.30	$1,189.30