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	$126.56	12.563%	$142.4597	$142.46	$142.45	$142.50
Purchase #2	$206.33	7.423%	$221.6459	$221.65	$221.65	$221.60
Purchase #3	$19.82	7.130%	$21.2332	$21.23	$21.25	$21.20
Purchase #4	$100.53	5.562%	$106.1215	$106.12	$106.10	$106.10
Purchase #5	$160.26	9.139%	$174.9062	$174.91	$174.90	$174.90
Purchase #6	$68.90	3.546%	$71.3432	$71.34	$71.35	$71.30
Purchase #7	$5.42	3.400%	$5.6043	$5.60	$5.60	$5.60
7 purchase totals =	$687.82		$743.3140	$743.31	$743.30	$743.20