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	$72.86	7.572%	$78.377	$78.38	$78.40	$78.40
Purchase #2	$129.81	4.613%	$135.7981	$135.80	$135.80	$135.80
Purchase #3	$60.87	9.772%	$66.8182	$66.82	$66.80	$66.80
Purchase #4	$154.53	8.817%	$168.1549	$168.15	$168.15	$168.20
Purchase #5	$89.90	8.874%	$97.8777	$97.88	$97.90	$97.90
Purchase #6	$236.66	12.147%	$265.4071	$265.41	$265.40	$265.40
Purchase #7	$104.33	11.254%	$116.0713	$116.07	$116.05	$116.10
7 purchase totals =	$848.96		$928.5043	$928.51	$928.50	$928.60