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	$68.50	4.792%	$71.7825	$71.78	$71.80	$71.80
Purchase #2	$217.93	8.402%	$236.2405	$236.24	$236.25	$236.20
Purchase #3	$119.68	6.197%	$127.0966	$127.10	$127.10	$127.10
Purchase #4	$59.86	4.242%	$62.3993	$62.40	$62.40	$62.40
Purchase #5	$244.50	13.426%	$277.3266	$277.33	$277.35	$277.30
Purchase #6	$95.76	3.275%	$98.8961	$98.90	$98.90	$98.90
Purchase #7	$141.25	13.361%	$160.1224	$160.12	$160.10	$160.10
7 purchase totals =	$947.48		$1,033.8640	$1,033.87	$1,033.90	$1,033.80