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	$91.76	7.427%	$98.575	$98.58	$98.60	$98.60
Purchase #2	$204.90	3.112%	$211.2765	$211.28	$211.30	$211.30
Purchase #3	$110.70	11.642%	$123.5877	$123.59	$123.60	$123.60
Purchase #4	$203.46	11.775%	$227.4174	$227.42	$227.40	$227.40
Purchase #5	$196.28	4.810%	$205.7211	$205.72	$205.70	$205.70
Purchase #6	$158.38	5.645%	$167.3206	$167.32	$167.30	$167.30
Purchase #7	$51.37	4.343%	$53.601	$53.60	$53.60	$53.60
7 purchase totals =	$1,016.85		$1,087.4993	$1,087.51	$1,087.50	$1,087.50