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	$13.70	8.645%	$14.8844	$14.88	$14.90	$14.90
Purchase #2	$195.54	11.318%	$217.6712	$217.67	$217.65	$217.70
Purchase #3	$80.78	10.455%	$89.2255	$89.23	$89.25	$89.20
Purchase #4	$74.98	10.608%	$82.9339	$82.93	$82.95	$82.90
Purchase #5	$181.29	4.603%	$189.6348	$189.63	$189.65	$189.60
Purchase #6	$224.40	7.164%	$240.476	$240.48	$240.50	$240.50
Purchase #7	$88.64	6.749%	$94.6223	$94.62	$94.60	$94.60
7 purchase totals =	$859.33		$929.4481	$929.44	$929.50	$929.40