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	$101.46	12.756%	$114.4022	$114.40	$114.40	$114.40
Purchase #2	$78.74	3.724%	$81.6723	$81.67	$81.65	$81.70
Purchase #3	$118.55	8.424%	$128.5367	$128.54	$128.55	$128.50
Purchase #4	$51.39	12.342%	$57.7326	$57.73	$57.75	$57.70
Purchase #5	$28.64	11.580%	$31.9565	$31.96	$31.95	$32.00
Purchase #6	$198.45	6.109%	$210.5733	$210.57	$210.55	$210.60
Purchase #7	$162.50	13.861%	$185.0241	$185.02	$185.00	$185.00
7 purchase totals =	$739.73		$809.8977	$809.89	$809.85	$809.90