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	$139.49	8.826%	$151.8014	$151.80	$151.80	$151.80
Purchase #2	$191.62	4.831%	$200.8772	$200.88	$200.90	$200.90
Purchase #3	$187.74	5.773%	$198.5782	$198.58	$198.60	$198.60
Purchase #4	$134.31	13.526%	$152.4768	$152.48	$152.50	$152.50
Purchase #5	$149.30	3.601%	$154.6763	$154.68	$154.70	$154.70
Purchase #6	$139.86	4.321%	$145.9034	$145.90	$145.90	$145.90
Purchase #7	$220.32	10.568%	$243.6034	$243.60	$243.60	$243.60
7 purchase totals =	$1,162.64		$1,247.9167	$1,247.92	$1,248.00	$1,248.00