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	$102.69	8.205%	$111.1157	$111.12	$111.10	$111.10
Purchase #2	$47.31	8.855%	$51.4993	$51.50	$51.50	$51.50
Purchase #3	$245.54	12.270%	$275.6678	$275.67	$275.65	$275.70
Purchase #4	$42.90	7.835%	$46.2612	$46.26	$46.25	$46.30
Purchase #5	$46.27	10.345%	$51.0566	$51.06	$51.05	$51.10
Purchase #6	$146.35	3.430%	$151.3698	$151.37	$151.35	$151.40
Purchase #7	$84.55	11.151%	$93.9782	$93.98	$94.00	$94.00
7 purchase totals =	$715.61		$780.9486	$780.96	$780.90	$781.10