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	$83.44	4.837%	$87.476	$87.48	$87.50	$87.50
Purchase #2	$190.76	10.251%	$210.3148	$210.31	$210.30	$210.30
Purchase #3	$63.89	3.684%	$66.2437	$66.24	$66.25	$66.20
Purchase #4	$198.61	9.722%	$217.9189	$217.92	$217.90	$217.90
Purchase #5	$87.34	10.106%	$96.1666	$96.17	$96.15	$96.20
Purchase #6	$118.33	6.867%	$126.4557	$126.46	$126.45	$126.50
Purchase #7	$35.32	13.672%	$40.149	$40.15	$40.15	$40.10
7 purchase totals =	$777.69		$844.7247	$844.73	$844.70	$844.70