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	$67.97	5.233%	$71.5269	$71.53	$71.55	$71.50
Purchase #2	$25.55	10.691%	$28.2816	$28.28	$28.30	$28.30
Purchase #3	$21.34	10.817%	$23.6483	$23.65	$23.65	$23.60
Purchase #4	$88.89	10.401%	$98.1354	$98.14	$98.15	$98.10
Purchase #5	$98.73	12.547%	$111.1177	$111.12	$111.10	$111.10
Purchase #6	$146.66	8.600%	$159.2728	$159.27	$159.25	$159.30
Purchase #7	$70.31	4.681%	$73.6012	$73.60	$73.60	$73.60
7 purchase totals =	$519.45		$565.5839	$565.59	$565.60	$565.50