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	$196.59	9.664%	$215.5885	$215.59	$215.60	$215.60
Purchase #2	$69.45	13.199%	$78.6167	$78.62	$78.60	$78.60
Purchase #3	$17.62	6.443%	$18.7553	$18.76	$18.75	$18.80
Purchase #4	$245.74	5.148%	$258.3907	$258.39	$258.40	$258.40
Purchase #5	$146.42	3.617%	$151.716	$151.72	$151.70	$151.70
Purchase #6	$185.55	11.132%	$206.2054	$206.21	$206.20	$206.20
Purchase #7	$113.46	12.467%	$127.6051	$127.61	$127.60	$127.60
7 purchase totals =	$974.83		$1,056.8777	$1,056.90	$1,056.85	$1,056.90