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	$91.41	11.800%	$102.1964	$102.20	$102.20	$102.20
Purchase #2	$75.31	3.372%	$77.8495	$77.85	$77.85	$77.80
Purchase #3	$79.43	12.405%	$89.2833	$89.28	$89.30	$89.30
Purchase #4	$112.91	11.259%	$125.6225	$125.62	$125.60	$125.60
Purchase #5	$164.64	12.579%	$185.3501	$185.35	$185.35	$185.40
Purchase #6	$139.79	4.115%	$145.5424	$145.54	$145.55	$145.50
Purchase #7	$219.87	6.147%	$233.3854	$233.39	$233.40	$233.40
7 purchase totals =	$883.36		$959.2296	$959.23	$959.25	$959.20