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	$171.91	7.290%	$184.4422	$184.44	$184.45	$184.40
Purchase #2	$59.54	10.864%	$66.0084	$66.01	$66.00	$66.00
Purchase #3	$193.29	12.481%	$217.4145	$217.41	$217.40	$217.40
Purchase #4	$195.79	12.330%	$219.9309	$219.93	$219.95	$219.90
Purchase #5	$51.96	8.647%	$56.453	$56.45	$56.45	$56.50
Purchase #6	$223.72	8.814%	$243.4387	$243.44	$243.45	$243.40
Purchase #7	$130.80	9.754%	$143.5582	$143.56	$143.55	$143.60
7 purchase totals =	$1,027.01		$1,131.2459	$1,131.24	$1,131.25	$1,131.20