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	$187.33	13.295%	$212.2355	$212.24	$212.25	$212.20
Purchase #2	$155.45	5.826%	$164.5065	$164.51	$164.50	$164.50
Purchase #3	$92.70	6.702%	$98.9128	$98.91	$98.90	$98.90
Purchase #4	$46.44	13.155%	$52.5492	$52.55	$52.55	$52.50
Purchase #5	$108.89	13.647%	$123.7502	$123.75	$123.75	$123.80
Purchase #6	$81.37	10.505%	$89.9179	$89.92	$89.90	$89.90
Purchase #7	$91.82	11.327%	$102.2205	$102.22	$102.20	$102.20
7 purchase totals =	$764.00		$844.0926	$844.10	$844.05	$844.00