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	$187.47	6.530%	$199.7118	$199.71	$199.70	$199.70
Purchase #2	$240.48	13.603%	$273.1925	$273.19	$273.20	$273.20
Purchase #3	$59.42	4.343%	$62.0006	$62.00	$62.00	$62.00
Purchase #4	$51.70	13.859%	$58.8651	$58.87	$58.85	$58.90
Purchase #5	$148.34	4.408%	$154.8788	$154.88	$154.90	$154.90
Purchase #6	$119.40	7.126%	$127.9084	$127.91	$127.90	$127.90
Purchase #7	$35.50	4.223%	$36.9992	$37.00	$37.00	$37.00
7 purchase totals =	$842.31		$913.5564	$913.56	$913.55	$913.60