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	$63.50	12.751%	$71.5969	$71.60	$71.60	$71.60
Purchase #2	$50.31	6.628%	$53.6445	$53.64	$53.65	$53.60
Purchase #3	$182.82	4.851%	$191.6886	$191.69	$191.70	$191.70
Purchase #4	$219.47	8.841%	$238.8733	$238.87	$238.85	$238.90
Purchase #5	$7.27	5.272%	$7.6533	$7.65	$7.65	$7.70
Purchase #6	$48.54	7.270%	$52.0689	$52.07	$52.05	$52.10
Purchase #7	$170.95	7.414%	$183.6242	$183.62	$183.60	$183.60
7 purchase totals =	$742.86		$799.1497	$799.14	$799.10	$799.20