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	$157.54	9.279%	$172.1581	$172.16	$172.15	$172.20
Purchase #2	$222.34	4.612%	$232.5943	$232.59	$232.60	$232.60
Purchase #3	$229.94	10.745%	$254.6471	$254.65	$254.65	$254.60
Purchase #4	$51.25	8.405%	$55.5576	$55.56	$55.55	$55.60
Purchase #5	$52.26	5.833%	$55.3083	$55.31	$55.30	$55.30
Purchase #6	$181.36	3.567%	$187.8291	$187.83	$187.85	$187.80
Purchase #7	$95.82	6.198%	$101.7589	$101.76	$101.75	$101.80
7 purchase totals =	$990.51		$1,059.8534	$1,059.86	$1,059.85	$1,059.90