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	$135.54	4.393%	$141.4943	$141.49	$141.50	$141.50
Purchase #2	$168.41	8.219%	$182.2516	$182.25	$182.25	$182.30
Purchase #3	$209.37	13.803%	$238.2693	$238.27	$238.25	$238.30
Purchase #4	$74.25	5.491%	$78.3271	$78.33	$78.35	$78.30
Purchase #5	$82.95	9.825%	$91.0998	$91.10	$91.10	$91.10
Purchase #6	$141.38	3.771%	$146.7114	$146.71	$146.70	$146.70
Purchase #7	$203.42	12.474%	$228.7946	$228.79	$228.80	$228.80
7 purchase totals =	$1,015.32		$1,106.9481	$1,106.94	$1,106.95	$1,107.00