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	$239.97	11.229%	$266.9162	$266.92	$266.90	$266.90
Purchase #2	$85.52	10.812%	$94.7664	$94.77	$94.75	$94.80
Purchase #3	$13.56	7.825%	$14.6211	$14.62	$14.60	$14.60
Purchase #4	$67.31	5.702%	$71.148	$71.15	$71.15	$71.10
Purchase #5	$49.53	7.872%	$53.429	$53.43	$53.45	$53.40
Purchase #6	$95.71	5.287%	$100.7702	$100.77	$100.75	$100.80
Purchase #7	$163.49	10.231%	$180.2167	$180.22	$180.20	$180.20
7 purchase totals =	$715.09		$781.8676	$781.88	$781.80	$781.80