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	$125.45	7.423%	$134.7622	$134.76	$134.75	$134.80
Purchase #2	$40.59	4.379%	$42.3674	$42.37	$42.35	$42.40
Purchase #3	$43.81	4.515%	$45.788	$45.79	$45.80	$45.80
Purchase #4	$235.43	11.595%	$262.7281	$262.73	$262.75	$262.70
Purchase #5	$94.72	11.577%	$105.6857	$105.69	$105.70	$105.70
Purchase #6	$209.63	5.844%	$221.8808	$221.88	$221.90	$221.90
Purchase #7	$204.41	5.752%	$216.1677	$216.17	$216.15	$216.20
7 purchase totals =	$954.04		$1,029.3799	$1,029.39	$1,029.40	$1,029.50