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	$94.85	7.759%	$102.2094	$102.21	$102.20	$102.20
Purchase #2	$242.48	9.515%	$265.552	$265.55	$265.55	$265.60
Purchase #3	$35.91	5.460%	$37.8707	$37.87	$37.85	$37.90
Purchase #4	$206.60	11.275%	$229.8942	$229.89	$229.90	$229.90
Purchase #5	$144.33	4.197%	$150.3875	$150.39	$150.40	$150.40
Purchase #6	$137.31	7.685%	$147.8623	$147.86	$147.85	$147.90
Purchase #7	$35.55	11.445%	$39.6187	$39.62	$39.60	$39.60
7 purchase totals =	$897.03		$973.3948	$973.39	$973.35	$973.50