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	$53.51	11.333%	$59.5743	$59.57	$59.55	$59.60
Purchase #2	$115.78	12.242%	$129.9538	$129.95	$129.95	$130.00
Purchase #3	$80.93	9.820%	$88.8773	$88.88	$88.90	$88.90
Purchase #4	$201.57	5.736%	$213.1321	$213.13	$213.15	$213.10
Purchase #5	$213.78	3.245%	$220.7172	$220.72	$220.70	$220.70
Purchase #6	$36.98	12.341%	$41.5437	$41.54	$41.55	$41.50
Purchase #7	$223.41	11.524%	$249.1558	$249.16	$249.15	$249.20
7 purchase totals =	$925.96		$1,002.9542	$1,002.95	$1,002.95	$1,003.00