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	$60.34	6.136%	$64.0425	$64.04	$64.05	$64.00
Purchase #2	$116.57	13.111%	$131.8535	$131.85	$131.85	$131.90
Purchase #3	$139.59	3.862%	$144.981	$144.98	$145.00	$145.00
Purchase #4	$94.82	5.639%	$100.1669	$100.17	$100.15	$100.20
Purchase #5	$67.59	9.147%	$73.7725	$73.77	$73.75	$73.80
Purchase #6	$134.84	5.514%	$142.2751	$142.28	$142.30	$142.30
Purchase #7	$92.93	11.341%	$103.4692	$103.47	$103.45	$103.50
7 purchase totals =	$706.68		$760.5607	$760.56	$760.55	$760.70