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	$52.45	11.359%	$58.4078	$58.41	$58.40	$58.40
Purchase #2	$16.72	10.819%	$18.5289	$18.53	$18.55	$18.50
Purchase #3	$59.75	3.427%	$61.7976	$61.80	$61.80	$61.80
Purchase #4	$172.91	7.307%	$185.5445	$185.54	$185.55	$185.50
Purchase #5	$77.31	8.289%	$83.7182	$83.72	$83.70	$83.70
Purchase #6	$56.97	10.183%	$62.7713	$62.77	$62.75	$62.80
Purchase #7	$16.32	12.207%	$18.3122	$18.31	$18.30	$18.30
7 purchase totals =	$452.43		$489.0805	$489.08	$489.05	$489.00