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	$90.42	7.439%	$97.1463	$97.15	$97.15	$97.10
Purchase #2	$31.29	10.732%	$34.648	$34.65	$34.65	$34.60
Purchase #3	$227.50	3.242%	$234.8756	$234.88	$234.90	$234.90
Purchase #4	$40.33	5.645%	$42.6066	$42.61	$42.60	$42.60
Purchase #5	$175.58	11.299%	$195.4188	$195.42	$195.40	$195.40
Purchase #6	$232.86	8.815%	$253.3866	$253.39	$253.40	$253.40
Purchase #7	$191.85	9.198%	$209.4964	$209.50	$209.50	$209.50
7 purchase totals =	$989.83		$1,067.5783	$1,067.60	$1,067.60	$1,067.50