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	$96.27	4.740%	$100.8332	$100.83	$100.85	$100.80
Purchase #2	$190.25	10.573%	$210.3651	$210.37	$210.35	$210.40
Purchase #3	$176.33	3.662%	$182.7872	$182.79	$182.80	$182.80
Purchase #4	$85.70	4.314%	$89.3971	$89.40	$89.40	$89.40
Purchase #5	$159.89	4.830%	$167.6127	$167.61	$167.60	$167.60
Purchase #6	$41.33	8.367%	$44.7881	$44.79	$44.80	$44.80
Purchase #7	$191.45	5.173%	$201.3537	$201.35	$201.35	$201.40
7 purchase totals =	$941.22		$997.1371	$997.14	$997.15	$997.20