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	$152.58	11.195%	$169.6613	$169.66	$169.65	$169.70
Purchase #2	$78.42	4.718%	$82.1199	$82.12	$82.10	$82.10
Purchase #3	$134.73	7.336%	$144.6138	$144.61	$144.60	$144.60
Purchase #4	$10.43	6.554%	$11.1136	$11.11	$11.10	$11.10
Purchase #5	$39.32	10.154%	$43.3126	$43.31	$43.30	$43.30
Purchase #6	$76.29	8.765%	$82.9768	$82.98	$83.00	$83.00
Purchase #7	$250.30	7.467%	$268.9899	$268.99	$269.00	$269.00
7 purchase totals =	$742.07		$802.7879	$802.78	$802.75	$802.80