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	$174.28	12.392%	$195.8768	$195.88	$195.90	$195.90
Purchase #2	$62.27	7.359%	$66.8524	$66.85	$66.85	$66.90
Purchase #3	$88.84	13.374%	$100.7215	$100.72	$100.70	$100.70
Purchase #4	$157.44	3.412%	$162.8119	$162.81	$162.80	$162.80
Purchase #5	$41.81	6.822%	$44.6623	$44.66	$44.65	$44.70
Purchase #6	$81.36	10.684%	$90.0525	$90.05	$90.05	$90.10
Purchase #7	$137.36	10.250%	$151.4394	$151.44	$151.45	$151.40
7 purchase totals =	$743.36		$812.4168	$812.41	$812.40	$812.50