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	$219.25	7.322%	$235.3035	$235.30	$235.30	$235.30
Purchase #2	$193.98	6.370%	$206.3365	$206.34	$206.35	$206.30
Purchase #3	$113.78	8.131%	$123.0315	$123.03	$123.05	$123.00
Purchase #4	$38.31	3.123%	$39.5064	$39.51	$39.50	$39.50
Purchase #5	$33.33	13.783%	$37.9239	$37.92	$37.90	$37.90
Purchase #6	$136.90	13.552%	$155.4527	$155.45	$155.45	$155.50
Purchase #7	$137.96	4.614%	$144.3255	$144.33	$144.35	$144.30
7 purchase totals =	$873.51		$941.8800	$941.88	$941.90	$941.80