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	$137.65	7.819%	$148.4129	$148.41	$148.40	$148.40
Purchase #2	$247.65	5.661%	$261.6695	$261.67	$261.65	$261.70
Purchase #3	$247.49	3.173%	$255.3429	$255.34	$255.35	$255.30
Purchase #4	$113.59	12.366%	$127.6365	$127.64	$127.65	$127.60
Purchase #5	$14.65	11.285%	$16.3033	$16.30	$16.30	$16.30
Purchase #6	$117.63	4.828%	$123.3092	$123.31	$123.30	$123.30
Purchase #7	$169.63	12.654%	$191.095	$191.10	$191.10	$191.10
7 purchase totals =	$1,048.29		$1,123.7693	$1,123.77	$1,123.75	$1,123.70