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	$182.52	3.229%	$188.4136	$188.41	$188.40	$188.40
Purchase #2	$88.58	13.768%	$100.7757	$100.78	$100.80	$100.80
Purchase #3	$192.73	7.224%	$206.6528	$206.65	$206.65	$206.70
Purchase #4	$52.45	3.410%	$54.2385	$54.24	$54.25	$54.20
Purchase #5	$224.86	4.333%	$234.6032	$234.60	$234.60	$234.60
Purchase #6	$159.82	4.150%	$166.4525	$166.45	$166.45	$166.50
Purchase #7	$173.25	10.732%	$191.8432	$191.84	$191.85	$191.80
7 purchase totals =	$1,074.21		$1,142.9795	$1,142.97	$1,143.00	$1,143.00