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	$174.69	12.395%	$196.3428	$196.34	$196.35	$196.30
Purchase #2	$213.31	4.590%	$223.1009	$223.10	$223.10	$223.10
Purchase #3	$127.72	10.275%	$140.8432	$140.84	$140.85	$140.80
Purchase #4	$105.37	11.773%	$117.7752	$117.78	$117.80	$117.80
Purchase #5	$123.65	6.668%	$131.895	$131.90	$131.90	$131.90
Purchase #6	$156.76	8.365%	$169.873	$169.87	$169.85	$169.90
Purchase #7	$245.39	4.550%	$256.5552	$256.56	$256.55	$256.60
7 purchase totals =	$1,146.89		$1,236.3853	$1,236.39	$1,236.40	$1,236.40