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	$73.83	11.368%	$82.223	$82.22	$82.20	$82.20
Purchase #2	$54.82	9.431%	$59.9901	$59.99	$60.00	$60.00
Purchase #3	$218.87	6.462%	$233.0134	$233.01	$233.00	$233.00
Purchase #4	$245.35	9.667%	$269.068	$269.07	$269.05	$269.10
Purchase #5	$8.87	12.536%	$9.9819	$9.98	$10.00	$10.00
Purchase #6	$120.39	6.333%	$128.0143	$128.01	$128.00	$128.00
Purchase #7	$38.75	11.763%	$43.3082	$43.31	$43.30	$43.30
7 purchase totals =	$760.88		$825.5989	$825.59	$825.55	$825.60