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	$59.96	13.250%	$67.9047	$67.90	$67.90	$67.90
Purchase #2	$228.77	4.334%	$238.6849	$238.68	$238.70	$238.70
Purchase #3	$30.44	7.647%	$32.7677	$32.77	$32.75	$32.80
Purchase #4	$108.76	6.378%	$115.6967	$115.70	$115.70	$115.70
Purchase #5	$232.80	6.556%	$248.0624	$248.06	$248.05	$248.10
Purchase #6	$91.27	12.735%	$102.8932	$102.89	$102.90	$102.90
Purchase #7	$245.90	6.766%	$262.5376	$262.54	$262.55	$262.50
7 purchase totals =	$997.90		$1,068.5472	$1,068.54	$1,068.55	$1,068.60