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	$207.41	10.851%	$229.9161	$229.92	$229.90	$229.90
Purchase #2	$166.53	13.686%	$189.3213	$189.32	$189.30	$189.30
Purchase #3	$207.40	6.291%	$220.4475	$220.45	$220.45	$220.40
Purchase #4	$61.72	3.301%	$63.7574	$63.76	$63.75	$63.80
Purchase #5	$203.73	9.315%	$222.7074	$222.71	$222.70	$222.70
Purchase #6	$46.37	11.845%	$51.8625	$51.86	$51.85	$51.90
Purchase #7	$208.30	6.348%	$221.5229	$221.52	$221.50	$221.50
7 purchase totals =	$1,101.46		$1,199.5351	$1,199.54	$1,199.45	$1,199.50