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	$137.82	10.623%	$152.4606	$152.46	$152.45	$152.50
Purchase #2	$127.47	13.781%	$145.0366	$145.04	$145.05	$145.00
Purchase #3	$187.45	12.757%	$211.363	$211.36	$211.35	$211.40
Purchase #4	$140.95	11.211%	$156.7519	$156.75	$156.75	$156.80
Purchase #5	$155.72	3.277%	$160.8229	$160.82	$160.80	$160.80
Purchase #6	$72.36	11.441%	$80.6387	$80.64	$80.65	$80.60
Purchase #7	$57.82	11.551%	$64.4988	$64.50	$64.50	$64.50
7 purchase totals =	$879.59		$971.5725	$971.57	$971.55	$971.60