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	$244.97	10.615%	$270.9736	$270.97	$270.95	$271.00
Purchase #2	$115.57	9.872%	$126.9791	$126.98	$127.00	$127.00
Purchase #3	$96.88	7.567%	$104.2109	$104.21	$104.20	$104.20
Purchase #4	$94.59	10.127%	$104.1691	$104.17	$104.15	$104.20
Purchase #5	$113.72	8.414%	$123.2884	$123.29	$123.30	$123.30
Purchase #6	$116.69	12.766%	$131.5866	$131.59	$131.60	$131.60
Purchase #7	$174.72	6.117%	$185.4076	$185.41	$185.40	$185.40
7 purchase totals =	$957.14		$1,046.6153	$1,046.62	$1,046.60	$1,046.70