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	$27.98	11.479%	$31.1918	$31.19	$31.20	$31.20
Purchase #2	$233.88	4.816%	$245.1437	$245.14	$245.15	$245.10
Purchase #3	$129.94	5.813%	$137.4934	$137.49	$137.50	$137.50
Purchase #4	$57.80	8.237%	$62.561	$62.56	$62.55	$62.60
Purchase #5	$225.31	13.177%	$254.9991	$255.00	$255.00	$255.00
Purchase #6	$88.33	7.240%	$94.7251	$94.73	$94.75	$94.70
Purchase #7	$242.37	11.154%	$269.4039	$269.40	$269.40	$269.40
7 purchase totals =	$1,005.61		$1,095.5180	$1,095.51	$1,095.55	$1,095.50