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	$209.36	7.107%	$224.2392	$224.24	$224.25	$224.20
Purchase #2	$92.45	12.496%	$104.0026	$104.00	$104.00	$104.00
Purchase #3	$162.36	3.541%	$168.1092	$168.11	$168.10	$168.10
Purchase #4	$61.50	7.709%	$66.241	$66.24	$66.25	$66.20
Purchase #5	$104.45	6.663%	$111.4095	$111.41	$111.40	$111.40
Purchase #6	$170.50	12.797%	$192.3189	$192.32	$192.30	$192.30
Purchase #7	$163.32	11.153%	$181.5351	$181.54	$181.55	$181.50
7 purchase totals =	$963.94		$1,047.8555	$1,047.86	$1,047.85	$1,047.70