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	$117.89	12.112%	$132.1688	$132.17	$132.15	$132.20
Purchase #2	$200.55	13.168%	$226.9584	$226.96	$226.95	$227.00
Purchase #3	$98.58	10.480%	$108.9112	$108.91	$108.90	$108.90
Purchase #4	$180.70	11.168%	$200.8806	$200.88	$200.90	$200.90
Purchase #5	$210.34	4.585%	$219.9841	$219.98	$220.00	$220.00
Purchase #6	$197.92	10.306%	$218.3176	$218.32	$218.30	$218.30
Purchase #7	$55.84	6.340%	$59.3803	$59.38	$59.40	$59.40
7 purchase totals =	$1,061.82		$1,166.6010	$1,166.60	$1,166.60	$1,166.70