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	$137.37	9.814%	$150.8515	$150.85	$150.85	$150.90
Purchase #2	$236.59	8.409%	$256.4849	$256.48	$256.50	$256.50
Purchase #3	$114.40	3.751%	$118.6911	$118.69	$118.70	$118.70
Purchase #4	$73.53	9.750%	$80.6992	$80.70	$80.70	$80.70
Purchase #5	$150.38	6.466%	$160.1036	$160.10	$160.10	$160.10
Purchase #6	$75.82	3.383%	$78.385	$78.39	$78.40	$78.40
Purchase #7	$94.92	11.662%	$105.9896	$105.99	$106.00	$106.00
7 purchase totals =	$883.01		$951.2049	$951.20	$951.25	$951.30