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	$163.61	7.836%	$176.4305	$176.43	$176.45	$176.40
Purchase #2	$155.59	3.648%	$161.2659	$161.27	$161.25	$161.30
Purchase #3	$225.85	5.746%	$238.8273	$238.83	$238.85	$238.80
Purchase #4	$88.55	9.519%	$96.9791	$96.98	$97.00	$97.00
Purchase #5	$70.36	3.165%	$72.5869	$72.59	$72.60	$72.60
Purchase #6	$191.37	10.311%	$211.1022	$211.10	$211.10	$211.10
Purchase #7	$125.91	12.834%	$142.0693	$142.07	$142.05	$142.10
7 purchase totals =	$1,021.24		$1,099.2612	$1,099.27	$1,099.30	$1,099.30