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	$97.31	4.345%	$101.5381	$101.54	$101.55	$101.50
Purchase #2	$200.97	7.786%	$216.6175	$216.62	$216.60	$216.60
Purchase #3	$37.75	6.272%	$40.1177	$40.12	$40.10	$40.10
Purchase #4	$178.65	11.126%	$198.5266	$198.53	$198.55	$198.50
Purchase #5	$187.57	13.327%	$212.5675	$212.57	$212.55	$212.60
Purchase #6	$17.89	4.656%	$18.723	$18.72	$18.70	$18.70
Purchase #7	$57.63	3.282%	$59.5214	$59.52	$59.50	$59.50
7 purchase totals =	$777.77		$847.6118	$847.62	$847.55	$847.50