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	$112.51	13.623%	$127.8372	$127.84	$127.85	$127.80
Purchase #2	$26.44	5.357%	$27.8564	$27.86	$27.85	$27.90
Purchase #3	$169.38	6.448%	$180.3016	$180.30	$180.30	$180.30
Purchase #4	$146.84	9.544%	$160.8544	$160.85	$160.85	$160.90
Purchase #5	$106.95	4.401%	$111.6569	$111.66	$111.65	$111.70
Purchase #6	$128.58	5.855%	$136.1084	$136.11	$136.10	$136.10
Purchase #7	$59.59	8.552%	$64.6861	$64.69	$64.70	$64.70
7 purchase totals =	$750.29		$809.3010	$809.31	$809.30	$809.40