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	$233.60	13.219%	$264.4796	$264.48	$264.50	$264.50
Purchase #2	$207.88	7.683%	$223.8514	$223.85	$223.85	$223.90
Purchase #3	$29.40	11.199%	$32.6925	$32.69	$32.70	$32.70
Purchase #4	$54.56	5.361%	$57.485	$57.49	$57.50	$57.50
Purchase #5	$145.32	5.434%	$153.2167	$153.22	$153.20	$153.20
Purchase #6	$249.79	7.858%	$269.4185	$269.42	$269.40	$269.40
Purchase #7	$59.45	9.649%	$65.1863	$65.19	$65.20	$65.20
7 purchase totals =	$980.00		$1,066.3300	$1,066.34	$1,066.35	$1,066.40