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	$207.63	7.584%	$223.3767	$223.38	$223.40	$223.40
Purchase #2	$192.83	13.179%	$218.2431	$218.24	$218.25	$218.20
Purchase #3	$100.29	11.246%	$111.5686	$111.57	$111.55	$111.60
Purchase #4	$98.93	12.531%	$111.3269	$111.33	$111.35	$111.30
Purchase #5	$51.54	6.526%	$54.9035	$54.90	$54.90	$54.90
Purchase #6	$70.96	13.670%	$80.6602	$80.66	$80.65	$80.70
Purchase #7	$149.44	11.562%	$166.7183	$166.72	$166.70	$166.70
7 purchase totals =	$871.62		$966.7973	$966.80	$966.80	$966.80