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	$54.82	11.786%	$61.2811	$61.28	$61.30	$61.30
Purchase #2	$96.85	3.634%	$100.3695	$100.37	$100.35	$100.40
Purchase #3	$128.66	4.418%	$134.3442	$134.34	$134.35	$134.30
Purchase #4	$213.99	7.724%	$230.5186	$230.52	$230.50	$230.50
Purchase #5	$91.48	4.601%	$95.689	$95.69	$95.70	$95.70
Purchase #6	$239.82	11.794%	$268.1044	$268.10	$268.10	$268.10
Purchase #7	$88.98	3.144%	$91.7775	$91.78	$91.80	$91.80
7 purchase totals =	$914.60		$982.0843	$982.08	$982.10	$982.10