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	$135.58	10.700%	$150.0871	$150.09	$150.10	$150.10
Purchase #2	$240.45	8.538%	$260.9796	$260.98	$261.00	$261.00
Purchase #3	$182.66	7.572%	$196.491	$196.49	$196.50	$196.50
Purchase #4	$172.28	13.347%	$195.2742	$195.27	$195.25	$195.30
Purchase #5	$7.56	4.627%	$7.9098	$7.91	$7.90	$7.90
Purchase #6	$180.90	4.439%	$188.9302	$188.93	$188.95	$188.90
Purchase #7	$95.31	3.634%	$98.7736	$98.77	$98.75	$98.80
7 purchase totals =	$1,014.74		$1,098.4455	$1,098.44	$1,098.45	$1,098.50