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	$100.61	12.487%	$113.1732	$113.17	$113.15	$113.20
Purchase #2	$220.42	13.410%	$249.9783	$249.98	$250.00	$250.00
Purchase #3	$20.77	6.403%	$22.0999	$22.10	$22.10	$22.10
Purchase #4	$180.73	5.627%	$190.8997	$190.90	$190.90	$190.90
Purchase #5	$203.44	9.373%	$222.5084	$222.51	$222.50	$222.50
Purchase #6	$30.70	3.862%	$31.8856	$31.89	$31.90	$31.90
Purchase #7	$209.66	11.723%	$234.2384	$234.24	$234.25	$234.20
7 purchase totals =	$966.33		$1,064.7835	$1,064.79	$1,064.80	$1,064.80