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	$34.66	3.862%	$35.9986	$36.00	$36.00	$36.00
Purchase #2	$174.98	12.398%	$196.674	$196.67	$196.65	$196.70
Purchase #3	$86.61	11.702%	$96.7451	$96.75	$96.75	$96.70
Purchase #4	$215.31	13.664%	$244.73	$244.73	$244.75	$244.70
Purchase #5	$234.61	7.212%	$251.5301	$251.53	$251.55	$251.50
Purchase #6	$34.46	9.867%	$37.8602	$37.86	$37.85	$37.90
Purchase #7	$56.49	4.448%	$59.0027	$59.00	$59.00	$59.00
7 purchase totals =	$837.12		$922.5407	$922.54	$922.55	$922.50