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	$72.72	10.656%	$80.469	$80.47	$80.45	$80.50
Purchase #2	$80.64	11.818%	$90.17	$90.17	$90.15	$90.20
Purchase #3	$161.65	9.568%	$177.1167	$177.12	$177.10	$177.10
Purchase #4	$166.98	3.394%	$172.6473	$172.65	$172.65	$172.60
Purchase #5	$95.48	9.543%	$104.5917	$104.59	$104.60	$104.60
Purchase #6	$217.39	9.498%	$238.0377	$238.04	$238.05	$238.00
Purchase #7	$64.92	11.699%	$72.515	$72.52	$72.50	$72.50
7 purchase totals =	$859.78		$935.5474	$935.56	$935.50	$935.50