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	$181.47	8.174%	$196.3034	$196.30	$196.30	$196.30
Purchase #2	$50.82	13.325%	$57.5918	$57.59	$57.60	$57.60
Purchase #3	$150.47	3.687%	$156.0178	$156.02	$156.00	$156.00
Purchase #4	$218.32	10.278%	$240.7589	$240.76	$240.75	$240.80
Purchase #5	$216.85	12.509%	$243.9758	$243.98	$244.00	$244.00
Purchase #6	$70.89	10.673%	$78.4561	$78.46	$78.45	$78.50
Purchase #7	$175.75	11.654%	$196.2319	$196.23	$196.25	$196.20
7 purchase totals =	$1,064.57		$1,169.3357	$1,169.34	$1,169.35	$1,169.40