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	$104.70	7.531%	$112.585	$112.59	$112.60	$112.60
Purchase #2	$54.89	7.753%	$59.1456	$59.15	$59.15	$59.10
Purchase #3	$27.82	4.125%	$28.9676	$28.97	$28.95	$29.00
Purchase #4	$27.29	13.504%	$30.9752	$30.98	$31.00	$31.00
Purchase #5	$80.94	13.434%	$91.8135	$91.81	$91.80	$91.80
Purchase #6	$105.99	7.304%	$113.7315	$113.73	$113.75	$113.70
Purchase #7	$168.62	12.244%	$189.2658	$189.27	$189.25	$189.30
7 purchase totals =	$570.25		$626.4842	$626.50	$626.50	$626.50