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	$221.59	13.251%	$250.9529	$250.95	$250.95	$251.00
Purchase #2	$107.49	4.794%	$112.6431	$112.64	$112.65	$112.60
Purchase #3	$87.33	13.694%	$99.289	$99.29	$99.30	$99.30
Purchase #4	$250.54	12.493%	$281.84	$281.84	$281.85	$281.80
Purchase #5	$139.88	8.679%	$152.0202	$152.02	$152.00	$152.00
Purchase #6	$101.79	6.446%	$108.3514	$108.35	$108.35	$108.40
Purchase #7	$108.82	3.770%	$112.9225	$112.92	$112.90	$112.90
7 purchase totals =	$1,017.44		$1,118.0191	$1,118.01	$1,118.00	$1,118.00