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	$118.74	6.834%	$126.8547	$126.85	$126.85	$126.90
Purchase #2	$173.26	10.527%	$191.4991	$191.50	$191.50	$191.50
Purchase #3	$28.63	9.557%	$31.3662	$31.37	$31.35	$31.40
Purchase #4	$235.79	8.402%	$255.6011	$255.60	$255.60	$255.60
Purchase #5	$102.27	6.758%	$109.1814	$109.18	$109.20	$109.20
Purchase #6	$59.42	3.563%	$61.5371	$61.54	$61.55	$61.50
Purchase #7	$47.40	3.460%	$49.04	$49.04	$49.05	$49.00
7 purchase totals =	$765.51		$825.0796	$825.08	$825.10	$825.10