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	$20.51	11.751%	$22.9201	$22.92	$22.90	$22.90
Purchase #2	$217.30	4.217%	$226.4635	$226.46	$226.45	$226.50
Purchase #3	$247.45	13.198%	$280.1085	$280.11	$280.10	$280.10
Purchase #4	$154.39	7.869%	$166.5389	$166.54	$166.55	$166.50
Purchase #5	$202.73	4.168%	$211.1798	$211.18	$211.20	$211.20
Purchase #6	$109.91	12.338%	$123.4707	$123.47	$123.45	$123.50
Purchase #7	$61.76	5.766%	$65.3211	$65.32	$65.30	$65.30
7 purchase totals =	$1,014.05		$1,096.0026	$1,096.00	$1,095.95	$1,096.00