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	$143.73	10.481%	$158.7943	$158.79	$158.80	$158.80
Purchase #2	$92.90	10.801%	$102.9341	$102.93	$102.95	$102.90
Purchase #3	$114.59	7.783%	$123.5085	$123.51	$123.50	$123.50
Purchase #4	$232.28	13.812%	$264.3625	$264.36	$264.35	$264.40
Purchase #5	$79.29	5.606%	$83.735	$83.74	$83.75	$83.70
Purchase #6	$160.26	11.365%	$178.4735	$178.47	$178.45	$178.50
Purchase #7	$171.71	5.784%	$181.6417	$181.64	$181.65	$181.60
7 purchase totals =	$994.76		$1,093.4496	$1,093.44	$1,093.45	$1,093.40