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	$156.42	4.536%	$163.5152	$163.52	$163.50	$163.50
Purchase #2	$156.30	10.197%	$172.2379	$172.24	$172.25	$172.20
Purchase #3	$211.72	8.370%	$229.441	$229.44	$229.45	$229.40
Purchase #4	$8.56	5.129%	$8.999	$9.00	$9.00	$9.00
Purchase #5	$141.28	10.404%	$155.9788	$155.98	$156.00	$156.00
Purchase #6	$120.72	8.540%	$131.0295	$131.03	$131.05	$131.00
Purchase #7	$214.65	13.629%	$243.9046	$243.90	$243.90	$243.90
7 purchase totals =	$1,009.65		$1,105.1060	$1,105.11	$1,105.15	$1,105.00