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	$245.58	5.530%	$259.1606	$259.16	$259.15	$259.20
Purchase #2	$98.61	11.447%	$109.8979	$109.90	$109.90	$109.90
Purchase #3	$52.77	11.870%	$59.0338	$59.03	$59.05	$59.00
Purchase #4	$138.31	9.276%	$151.1396	$151.14	$151.15	$151.10
Purchase #5	$105.64	3.347%	$109.1758	$109.18	$109.20	$109.20
Purchase #6	$92.36	6.568%	$98.4262	$98.43	$98.45	$98.40
Purchase #7	$94.97	13.356%	$107.6542	$107.65	$107.65	$107.70
7 purchase totals =	$828.24		$894.4881	$894.49	$894.55	$894.50