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	$162.37	13.468%	$184.238	$184.24	$184.25	$184.20
Purchase #2	$207.33	7.279%	$222.4216	$222.42	$222.40	$222.40
Purchase #3	$138.85	6.777%	$148.2599	$148.26	$148.25	$148.30
Purchase #4	$18.25	11.662%	$20.3783	$20.38	$20.40	$20.40
Purchase #5	$163.40	5.197%	$171.8919	$171.89	$171.90	$171.90
Purchase #6	$116.50	7.212%	$124.902	$124.90	$124.90	$124.90
Purchase #7	$56.80	10.263%	$62.6294	$62.63	$62.65	$62.60
7 purchase totals =	$863.50		$934.7211	$934.72	$934.75	$934.70