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	$51.71	13.771%	$58.831	$58.83	$58.85	$58.80
Purchase #2	$100.92	7.588%	$108.5778	$108.58	$108.60	$108.60
Purchase #3	$77.62	10.247%	$85.5737	$85.57	$85.55	$85.60
Purchase #4	$152.63	8.761%	$166.0019	$166.00	$166.00	$166.00
Purchase #5	$102.44	10.147%	$112.8346	$112.83	$112.85	$112.80
Purchase #6	$236.26	4.443%	$246.757	$246.76	$246.75	$246.80
Purchase #7	$215.74	10.454%	$238.2935	$238.29	$238.30	$238.30
7 purchase totals =	$937.32		$1,016.8695	$1,016.86	$1,016.90	$1,016.90