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	$100.66	11.213%	$111.947	$111.95	$111.95	$111.90
Purchase #2	$41.27	11.568%	$46.0441	$46.04	$46.05	$46.00
Purchase #3	$59.81	13.610%	$67.9501	$67.95	$67.95	$68.00
Purchase #4	$241.74	11.115%	$268.6094	$268.61	$268.60	$268.60
Purchase #5	$49.36	11.854%	$55.2111	$55.21	$55.20	$55.20
Purchase #6	$159.40	7.206%	$170.8864	$170.89	$170.90	$170.90
Purchase #7	$56.96	3.660%	$59.0447	$59.04	$59.05	$59.00
7 purchase totals =	$709.20		$779.6928	$779.69	$779.70	$779.60