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	$105.32	9.104%	$114.9083	$114.91	$114.90	$114.90
Purchase #2	$65.49	10.531%	$72.3868	$72.39	$72.40	$72.40
Purchase #3	$127.72	10.790%	$141.501	$141.50	$141.50	$141.50
Purchase #4	$245.32	12.686%	$276.4413	$276.44	$276.45	$276.40
Purchase #5	$125.49	12.534%	$141.2189	$141.22	$141.20	$141.20
Purchase #6	$216.26	11.135%	$240.3406	$240.34	$240.35	$240.30
Purchase #7	$61.56	7.314%	$66.0625	$66.06	$66.05	$66.10
7 purchase totals =	$947.16		$1,052.8594	$1,052.86	$1,052.85	$1,052.80