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	$103.46	9.470%	$113.2577	$113.26	$113.25	$113.30
Purchase #2	$28.65	13.582%	$32.5412	$32.54	$32.55	$32.50
Purchase #3	$226.81	12.393%	$254.9186	$254.92	$254.90	$254.90
Purchase #4	$148.91	13.643%	$169.2258	$169.23	$169.25	$169.20
Purchase #5	$101.39	3.393%	$104.8302	$104.83	$104.85	$104.80
Purchase #6	$191.60	11.554%	$213.7375	$213.74	$213.75	$213.70
Purchase #7	$175.85	12.596%	$198.0001	$198.00	$198.00	$198.00
7 purchase totals =	$976.67		$1,086.5111	$1,086.52	$1,086.55	$1,086.40