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	$173.39	9.566%	$189.9765	$189.98	$190.00	$190.00
Purchase #2	$125.66	6.207%	$133.4597	$133.46	$133.45	$133.50
Purchase #3	$40.61	9.819%	$44.5975	$44.60	$44.60	$44.60
Purchase #4	$158.41	10.403%	$174.8894	$174.89	$174.90	$174.90
Purchase #5	$184.57	8.278%	$199.8487	$199.85	$199.85	$199.80
Purchase #6	$96.36	4.418%	$100.6172	$100.62	$100.60	$100.60
Purchase #7	$187.78	13.310%	$212.7735	$212.77	$212.75	$212.80
7 purchase totals =	$966.78		$1,056.1625	$1,056.17	$1,056.15	$1,056.20