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	$82.75	8.368%	$89.6745	$89.67	$89.65	$89.70
Purchase #2	$59.66	9.391%	$65.2627	$65.26	$65.25	$65.30
Purchase #3	$105.37	7.655%	$113.4361	$113.44	$113.45	$113.40
Purchase #4	$74.95	10.693%	$82.9644	$82.96	$82.95	$83.00
Purchase #5	$178.71	8.534%	$193.9611	$193.96	$193.95	$194.00
Purchase #6	$16.71	9.599%	$18.314	$18.31	$18.30	$18.30
Purchase #7	$211.32	3.409%	$218.5239	$218.52	$218.50	$218.50
7 purchase totals =	$729.47		$782.1367	$782.12	$782.05	$782.20