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	$206.63	7.632%	$222.4	$222.40	$222.40	$222.40
Purchase #2	$12.72	9.135%	$13.882	$13.88	$13.90	$13.90
Purchase #3	$40.93	6.840%	$43.7296	$43.73	$43.75	$43.70
Purchase #4	$174.91	5.727%	$184.9271	$184.93	$184.95	$184.90
Purchase #5	$190.77	12.829%	$215.2439	$215.24	$215.25	$215.20
Purchase #6	$138.31	5.452%	$145.8507	$145.85	$145.85	$145.90
Purchase #7	$7.33	12.234%	$8.2268	$8.23	$8.25	$8.20
7 purchase totals =	$771.60		$834.2601	$834.26	$834.35	$834.20