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	$81.61	6.437%	$86.8632	$86.86	$86.85	$86.90
Purchase #2	$128.28	6.234%	$136.277	$136.28	$136.30	$136.30
Purchase #3	$134.48	6.290%	$142.9388	$142.94	$142.95	$142.90
Purchase #4	$7.29	4.223%	$7.5979	$7.60	$7.60	$7.60
Purchase #5	$156.98	9.874%	$172.4802	$172.48	$172.50	$172.50
Purchase #6	$39.27	11.614%	$43.8308	$43.83	$43.85	$43.80
Purchase #7	$140.77	5.512%	$148.5292	$148.53	$148.55	$148.50
7 purchase totals =	$688.68		$738.5171	$738.52	$738.60	$738.50