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	$67.42	9.392%	$73.7521	$73.75	$73.75	$73.80
Purchase #2	$104.72	7.866%	$112.9573	$112.96	$112.95	$113.00
Purchase #3	$38.36	7.331%	$41.1722	$41.17	$41.15	$41.20
Purchase #4	$130.54	11.400%	$145.4216	$145.42	$145.40	$145.40
Purchase #5	$105.62	5.704%	$111.6446	$111.64	$111.65	$111.60
Purchase #6	$196.27	13.239%	$222.2542	$222.25	$222.25	$222.30
Purchase #7	$147.59	13.692%	$167.798	$167.80	$167.80	$167.80
7 purchase totals =	$790.52		$875.0000	$874.99	$874.95	$875.10