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	$18.66	4.274%	$19.4575	$19.46	$19.45	$19.50
Purchase #2	$61.67	3.175%	$63.628	$63.63	$63.65	$63.60
Purchase #3	$163.60	8.868%	$178.108	$178.11	$178.10	$178.10
Purchase #4	$49.37	11.165%	$54.8822	$54.88	$54.90	$54.90
Purchase #5	$104.87	5.873%	$111.029	$111.03	$111.05	$111.00
Purchase #6	$204.91	7.373%	$220.018	$220.02	$220.00	$220.00
Purchase #7	$57.53	3.212%	$59.3779	$59.38	$59.40	$59.40
7 purchase totals =	$660.61		$706.5006	$706.51	$706.55	$706.50