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	$64.33	11.154%	$71.5054	$71.51	$71.50	$71.50
Purchase #2	$64.92	7.508%	$69.7942	$69.79	$69.80	$69.80
Purchase #3	$75.43	13.202%	$85.3883	$85.39	$85.40	$85.40
Purchase #4	$72.31	5.870%	$76.5546	$76.55	$76.55	$76.60
Purchase #5	$63.67	11.782%	$71.1716	$71.17	$71.15	$71.20
Purchase #6	$106.29	3.745%	$110.2706	$110.27	$110.25	$110.30
Purchase #7	$101.83	7.649%	$109.619	$109.62	$109.60	$109.60
7 purchase totals =	$548.78		$594.3037	$594.30	$594.25	$594.40