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	$161.51	4.627%	$168.9831	$168.98	$169.00	$169.00
Purchase #2	$77.55	10.326%	$85.5578	$85.56	$85.55	$85.60
Purchase #3	$92.49	4.265%	$96.4347	$96.43	$96.45	$96.40
Purchase #4	$159.38	11.535%	$177.7645	$177.76	$177.75	$177.80
Purchase #5	$209.93	7.480%	$225.6328	$225.63	$225.65	$225.60
Purchase #6	$222.27	8.842%	$241.9231	$241.92	$241.90	$241.90
Purchase #7	$141.50	6.234%	$150.3211	$150.32	$150.30	$150.30
7 purchase totals =	$1,064.63		$1,146.6171	$1,146.60	$1,146.60	$1,146.60