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	$130.45	13.381%	$147.9055	$147.91	$147.90	$147.90
Purchase #2	$165.95	6.116%	$176.0995	$176.10	$176.10	$176.10
Purchase #3	$72.74	13.362%	$82.4595	$82.46	$82.45	$82.50
Purchase #4	$20.52	13.524%	$23.2951	$23.30	$23.30	$23.30
Purchase #5	$31.27	11.702%	$34.9292	$34.93	$34.95	$34.90
Purchase #6	$123.59	3.149%	$127.4818	$127.48	$127.50	$127.50
Purchase #7	$16.31	7.521%	$17.5367	$17.54	$17.55	$17.50
7 purchase totals =	$560.83		$609.7073	$609.72	$609.75	$609.70