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	$141.78	6.204%	$150.576	$150.58	$150.60	$150.60
Purchase #2	$195.69	10.638%	$216.5075	$216.51	$216.50	$216.50
Purchase #3	$188.26	12.319%	$211.4517	$211.45	$211.45	$211.50
Purchase #4	$171.70	5.694%	$181.4766	$181.48	$181.50	$181.50
Purchase #5	$220.62	10.380%	$243.5204	$243.52	$243.50	$243.50
Purchase #6	$124.38	4.526%	$130.0094	$130.01	$130.00	$130.00
Purchase #7	$38.49	6.246%	$40.8941	$40.89	$40.90	$40.90
7 purchase totals =	$1,080.92		$1,174.4357	$1,174.44	$1,174.45	$1,174.50