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	$244.86	4.481%	$255.8322	$255.83	$255.85	$255.80
Purchase #2	$185.49	11.215%	$206.2927	$206.29	$206.30	$206.30
Purchase #3	$138.33	8.654%	$150.3011	$150.30	$150.30	$150.30
Purchase #4	$94.25	7.609%	$101.4215	$101.42	$101.40	$101.40
Purchase #5	$155.80	10.695%	$172.4628	$172.46	$172.45	$172.50
Purchase #6	$153.55	6.128%	$162.9595	$162.96	$162.95	$163.00
Purchase #7	$136.63	3.573%	$141.5118	$141.51	$141.50	$141.50
7 purchase totals =	$1,108.91		$1,190.7816	$1,190.77	$1,190.75	$1,190.80