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	$46.95	4.380%	$49.0064	$49.01	$49.00	$49.00
Purchase #2	$248.67	10.600%	$275.029	$275.03	$275.05	$275.00
Purchase #3	$114.40	4.172%	$119.1728	$119.17	$119.15	$119.20
Purchase #4	$223.77	6.389%	$238.0667	$238.07	$238.05	$238.10
Purchase #5	$189.63	8.657%	$206.0463	$206.05	$206.05	$206.00
Purchase #6	$116.39	6.408%	$123.8483	$123.85	$123.85	$123.80
Purchase #7	$179.64	3.446%	$185.8304	$185.83	$185.85	$185.80
7 purchase totals =	$1,119.45		$1,196.9999	$1,197.01	$1,197.00	$1,196.90