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	$170.28	10.148%	$187.56	$187.56	$187.55	$187.60
Purchase #2	$133.59	7.383%	$143.4529	$143.45	$143.45	$143.50
Purchase #3	$134.49	10.374%	$148.442	$148.44	$148.45	$148.40
Purchase #4	$244.55	5.141%	$257.1223	$257.12	$257.10	$257.10
Purchase #5	$208.88	7.663%	$224.8865	$224.89	$224.90	$224.90
Purchase #6	$33.72	3.291%	$34.8297	$34.83	$34.85	$34.80
Purchase #7	$49.53	10.747%	$54.853	$54.85	$54.85	$54.90
7 purchase totals =	$975.04		$1,051.1464	$1,051.14	$1,051.15	$1,051.20