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	$167.35	4.501%	$174.8824	$174.88	$174.90	$174.90
Purchase #2	$213.54	13.720%	$242.8377	$242.84	$242.85	$242.80
Purchase #3	$93.61	7.745%	$100.8601	$100.86	$100.85	$100.90
Purchase #4	$93.73	9.437%	$102.5753	$102.58	$102.60	$102.60
Purchase #5	$247.42	13.468%	$280.7425	$280.74	$280.75	$280.70
Purchase #6	$92.69	5.631%	$97.9094	$97.91	$97.90	$97.90
Purchase #7	$111.79	10.159%	$123.1467	$123.15	$123.15	$123.10
7 purchase totals =	$1,020.13		$1,122.9541	$1,122.96	$1,123.00	$1,122.90