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	$77.64	6.405%	$82.6128	$82.61	$82.60	$82.60
Purchase #2	$13.91	6.317%	$14.7887	$14.79	$14.80	$14.80
Purchase #3	$156.38	10.362%	$172.5841	$172.58	$172.60	$172.60
Purchase #4	$58.43	6.588%	$62.2794	$62.28	$62.30	$62.30
Purchase #5	$148.30	6.507%	$157.9499	$157.95	$157.95	$157.90
Purchase #6	$202.35	13.473%	$229.6126	$229.61	$229.60	$229.60
Purchase #7	$77.27	4.700%	$80.9017	$80.90	$80.90	$80.90
7 purchase totals =	$734.28		$800.7292	$800.72	$800.75	$800.70