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	$103.53	4.105%	$107.7799	$107.78	$107.80	$107.80
Purchase #2	$43.66	7.396%	$46.8891	$46.89	$46.90	$46.90
Purchase #3	$217.64	6.559%	$231.915	$231.92	$231.90	$231.90
Purchase #4	$59.71	3.171%	$61.6034	$61.60	$61.60	$61.60
Purchase #5	$245.81	11.371%	$273.7611	$273.76	$273.75	$273.80
Purchase #6	$72.84	12.764%	$82.1373	$82.14	$82.15	$82.10
Purchase #7	$210.42	6.274%	$223.6218	$223.62	$223.60	$223.60
7 purchase totals =	$953.61		$1,027.7076	$1,027.71	$1,027.70	$1,027.70