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	$215.72	10.472%	$238.3102	$238.31	$238.30	$238.30
Purchase #2	$63.99	7.803%	$68.9831	$68.98	$69.00	$69.00
Purchase #3	$136.48	3.179%	$140.8187	$140.82	$140.80	$140.80
Purchase #4	$93.96	6.662%	$100.2196	$100.22	$100.20	$100.20
Purchase #5	$150.87	10.367%	$166.5107	$166.51	$166.50	$166.50
Purchase #6	$189.37	11.543%	$211.229	$211.23	$211.25	$211.20
Purchase #7	$83.46	8.178%	$90.2854	$90.29	$90.30	$90.30
7 purchase totals =	$933.85		$1,016.3567	$1,016.36	$1,016.35	$1,016.30