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	$240.29	6.280%	$255.3802	$255.38	$255.40	$255.40
Purchase #2	$89.38	6.320%	$95.0288	$95.03	$95.05	$95.00
Purchase #3	$219.97	11.474%	$245.2094	$245.21	$245.20	$245.20
Purchase #4	$21.29	12.407%	$23.9315	$23.93	$23.95	$23.90
Purchase #5	$245.42	11.760%	$274.2814	$274.28	$274.30	$274.30
Purchase #6	$59.39	4.662%	$62.1588	$62.16	$62.15	$62.20
Purchase #7	$141.32	8.580%	$153.4453	$153.45	$153.45	$153.40
7 purchase totals =	$1,017.06		$1,109.4354	$1,109.44	$1,109.50	$1,109.40