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	$212.43	6.657%	$226.5715	$226.57	$226.55	$226.60
Purchase #2	$83.32	6.355%	$88.615	$88.62	$88.60	$88.60
Purchase #3	$19.50	9.136%	$21.2815	$21.28	$21.30	$21.30
Purchase #4	$136.39	6.602%	$145.3945	$145.39	$145.40	$145.40
Purchase #5	$84.72	6.232%	$89.9998	$90.00	$90.00	$90.00
Purchase #6	$56.42	5.507%	$59.527	$59.53	$59.55	$59.50
Purchase #7	$108.67	11.253%	$120.8986	$120.90	$120.90	$120.90
7 purchase totals =	$701.45		$752.2879	$752.29	$752.30	$752.30