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	$101.87	3.763%	$105.7034	$105.70	$105.70	$105.70
Purchase #2	$238.33	7.540%	$256.3001	$256.30	$256.30	$256.30
Purchase #3	$189.48	3.442%	$196.0019	$196.00	$196.00	$196.00
Purchase #4	$159.56	5.557%	$168.4267	$168.43	$168.45	$168.40
Purchase #5	$49.32	12.686%	$55.5767	$55.58	$55.60	$55.60
Purchase #6	$106.83	8.809%	$116.2407	$116.24	$116.25	$116.20
Purchase #7	$90.45	5.227%	$95.1778	$95.18	$95.20	$95.20
7 purchase totals =	$935.84		$993.4273	$993.43	$993.50	$993.40