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	$99.48	10.383%	$109.809	$109.81	$109.80	$109.80
Purchase #2	$218.57	12.434%	$245.747	$245.75	$245.75	$245.70
Purchase #3	$31.41	8.559%	$34.0984	$34.10	$34.10	$34.10
Purchase #4	$44.32	3.403%	$45.8282	$45.83	$45.85	$45.80
Purchase #5	$71.64	12.554%	$80.6337	$80.63	$80.65	$80.60
Purchase #6	$166.31	7.379%	$178.582	$178.58	$178.60	$178.60
Purchase #7	$87.46	12.231%	$98.1572	$98.16	$98.15	$98.20
7 purchase totals =	$719.19		$792.8555	$792.86	$792.90	$792.80