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	$85.98	5.873%	$91.0296	$91.03	$91.05	$91.00
Purchase #2	$249.48	13.383%	$282.8679	$282.87	$282.85	$282.90
Purchase #3	$99.39	3.455%	$102.8239	$102.82	$102.80	$102.80
Purchase #4	$50.31	4.322%	$52.4844	$52.48	$52.50	$52.50
Purchase #5	$222.40	6.437%	$236.7159	$236.72	$236.70	$236.70
Purchase #6	$171.67	8.288%	$185.898	$185.90	$185.90	$185.90
Purchase #7	$194.44	8.313%	$210.6038	$210.60	$210.60	$210.60
7 purchase totals =	$1,073.67		$1,162.4235	$1,162.42	$1,162.40	$1,162.40