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	$69.32	13.388%	$78.6006	$78.60	$78.60	$78.60
Purchase #2	$6.79	3.178%	$7.0058	$7.01	$7.00	$7.00
Purchase #3	$190.70	11.418%	$212.4741	$212.47	$212.45	$212.50
Purchase #4	$184.84	3.278%	$190.8991	$190.90	$190.90	$190.90
Purchase #5	$65.83	3.601%	$68.2005	$68.20	$68.20	$68.20
Purchase #6	$156.36	11.478%	$174.307	$174.31	$174.30	$174.30
Purchase #7	$195.98	13.187%	$221.8239	$221.82	$221.80	$221.80
7 purchase totals =	$869.82		$953.3110	$953.31	$953.25	$953.30