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	$162.42	6.243%	$172.5599	$172.56	$172.55	$172.60
Purchase #2	$157.28	9.629%	$172.4245	$172.42	$172.40	$172.40
Purchase #3	$76.37	4.554%	$79.8479	$79.85	$79.85	$79.80
Purchase #4	$196.38	3.697%	$203.6402	$203.64	$203.65	$203.60
Purchase #5	$86.81	4.213%	$90.4673	$90.47	$90.45	$90.50
Purchase #6	$198.27	6.313%	$210.7868	$210.79	$210.80	$210.80
Purchase #7	$179.28	8.716%	$194.906	$194.91	$194.90	$194.90
7 purchase totals =	$1,056.81		$1,124.6326	$1,124.64	$1,124.60	$1,124.60