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	$87.46	9.814%	$96.0433	$96.04	$96.05	$96.00
Purchase #2	$250.90	10.864%	$278.1578	$278.16	$278.15	$278.20
Purchase #3	$97.95	12.151%	$109.8519	$109.85	$109.85	$109.90
Purchase #4	$226.52	6.145%	$240.4397	$240.44	$240.45	$240.40
Purchase #5	$99.47	9.697%	$109.1156	$109.12	$109.10	$109.10
Purchase #6	$120.44	11.368%	$134.1316	$134.13	$134.15	$134.10
Purchase #7	$76.63	11.582%	$85.5053	$85.51	$85.50	$85.50
7 purchase totals =	$959.37		$1,053.2452	$1,053.25	$1,053.25	$1,053.20