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	$166.60	7.835%	$179.6531	$179.65	$179.65	$179.70
Purchase #2	$221.42	9.647%	$242.7804	$242.78	$242.80	$242.80
Purchase #3	$105.77	3.384%	$109.3493	$109.35	$109.35	$109.30
Purchase #4	$106.77	4.804%	$111.8992	$111.90	$111.90	$111.90
Purchase #5	$62.31	12.655%	$70.1953	$70.20	$70.20	$70.20
Purchase #6	$168.63	13.675%	$191.6902	$191.69	$191.70	$191.70
Purchase #7	$138.72	7.347%	$148.9118	$148.91	$148.90	$148.90
7 purchase totals =	$970.22		$1,054.4793	$1,054.48	$1,054.50	$1,054.50