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	$150.34	12.201%	$168.683	$168.68	$168.70	$168.70
Purchase #2	$168.41	3.330%	$174.0181	$174.02	$174.00	$174.00
Purchase #3	$32.89	4.236%	$34.2832	$34.28	$34.30	$34.30
Purchase #4	$57.49	6.583%	$61.2746	$61.27	$61.25	$61.30
Purchase #5	$141.44	12.350%	$158.9078	$158.91	$158.90	$158.90
Purchase #6	$233.27	11.624%	$260.3853	$260.39	$260.40	$260.40
Purchase #7	$219.85	4.556%	$229.8664	$229.87	$229.85	$229.90
7 purchase totals =	$1,003.69		$1,087.4184	$1,087.42	$1,087.40	$1,087.50