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	$163.35	5.705%	$172.6691	$172.67	$172.65	$172.70
Purchase #2	$59.29	4.794%	$62.1324	$62.13	$62.15	$62.10
Purchase #3	$100.96	13.716%	$114.8077	$114.81	$114.80	$114.80
Purchase #4	$59.77	7.282%	$64.1225	$64.12	$64.10	$64.10
Purchase #5	$38.82	5.632%	$41.0063	$41.01	$41.00	$41.00
Purchase #6	$54.95	11.702%	$61.3802	$61.38	$61.40	$61.40
Purchase #7	$41.96	7.394%	$45.0625	$45.06	$45.05	$45.10
7 purchase totals =	$519.10		$561.1807	$561.18	$561.15	$561.20