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	$96.65	4.114%	$100.6262	$100.63	$100.65	$100.60
Purchase #2	$117.45	7.504%	$126.2634	$126.26	$126.25	$126.30
Purchase #3	$167.56	8.839%	$182.3706	$182.37	$182.35	$182.40
Purchase #4	$164.45	3.419%	$170.0725	$170.07	$170.05	$170.10
Purchase #5	$190.33	10.848%	$210.977	$210.98	$211.00	$211.00
Purchase #6	$89.85	6.392%	$95.5932	$95.59	$95.60	$95.60
Purchase #7	$117.46	13.642%	$133.4839	$133.48	$133.50	$133.50
7 purchase totals =	$943.75		$1,019.3868	$1,019.38	$1,019.40	$1,019.50