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	$238.69	8.851%	$259.8165	$259.82	$259.80	$259.80
Purchase #2	$121.35	9.792%	$133.2326	$133.23	$133.25	$133.20
Purchase #3	$40.67	7.628%	$43.7723	$43.77	$43.75	$43.80
Purchase #4	$142.48	4.166%	$148.4157	$148.42	$148.40	$148.40
Purchase #5	$229.47	6.510%	$244.4085	$244.41	$244.40	$244.40
Purchase #6	$9.93	10.524%	$10.975	$10.98	$11.00	$11.00
Purchase #7	$162.54	5.468%	$171.4277	$171.43	$171.45	$171.40
7 purchase totals =	$945.13		$1,012.0483	$1,012.06	$1,012.05	$1,012.00