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	$200.31	7.347%	$215.0268	$215.03	$215.05	$215.00
Purchase #2	$245.47	11.401%	$273.456	$273.46	$273.45	$273.50
Purchase #3	$7.35	8.139%	$7.9482	$7.95	$7.95	$7.90
Purchase #4	$74.36	6.754%	$79.3823	$79.38	$79.40	$79.40
Purchase #5	$17.56	6.843%	$18.7616	$18.76	$18.75	$18.80
Purchase #6	$37.79	11.251%	$42.0418	$42.04	$42.05	$42.00
Purchase #7	$35.57	5.342%	$37.4701	$37.47	$37.45	$37.50
7 purchase totals =	$618.41		$674.0868	$674.09	$674.10	$674.10