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	$212.57	4.687%	$222.5332	$222.53	$222.55	$222.50
Purchase #2	$124.39	3.145%	$128.3021	$128.30	$128.30	$128.30
Purchase #3	$140.77	7.589%	$151.453	$151.45	$151.45	$151.50
Purchase #4	$95.50	4.230%	$99.5397	$99.54	$99.55	$99.50
Purchase #5	$207.85	3.688%	$215.5155	$215.52	$215.50	$215.50
Purchase #6	$47.46	3.728%	$49.2293	$49.23	$49.25	$49.20
Purchase #7	$184.51	4.609%	$193.0141	$193.01	$193.00	$193.00
7 purchase totals =	$1,013.05		$1,059.5869	$1,059.58	$1,059.60	$1,059.50