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	$203.80	9.192%	$222.5333	$222.53	$222.55	$222.50
Purchase #2	$49.67	10.872%	$55.0701	$55.07	$55.05	$55.10
Purchase #3	$80.81	12.709%	$91.0801	$91.08	$91.10	$91.10
Purchase #4	$84.26	5.189%	$88.6323	$88.63	$88.65	$88.60
Purchase #5	$90.56	4.321%	$94.4731	$94.47	$94.45	$94.50
Purchase #6	$93.65	13.339%	$106.142	$106.14	$106.15	$106.10
Purchase #7	$157.81	6.415%	$167.9335	$167.93	$167.95	$167.90
7 purchase totals =	$760.56		$825.8644	$825.85	$825.90	$825.80