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	$57.30	3.358%	$59.2241	$59.22	$59.20	$59.20
Purchase #2	$96.97	3.232%	$100.1041	$100.10	$100.10	$100.10
Purchase #3	$228.61	11.192%	$254.196	$254.20	$254.20	$254.20
Purchase #4	$135.49	11.822%	$151.5076	$151.51	$151.50	$151.50
Purchase #5	$85.99	12.626%	$96.8471	$96.85	$96.85	$96.80
Purchase #6	$19.37	3.372%	$20.0232	$20.02	$20.00	$20.00
Purchase #7	$216.82	5.429%	$228.5912	$228.59	$228.60	$228.60
7 purchase totals =	$840.55		$910.4933	$910.49	$910.45	$910.40