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	$191.95	4.357%	$200.3133	$200.31	$200.30	$200.30
Purchase #2	$64.58	13.438%	$73.2583	$73.26	$73.25	$73.30
Purchase #3	$72.88	5.620%	$76.9759	$76.98	$77.00	$77.00
Purchase #4	$81.73	10.680%	$90.4588	$90.46	$90.45	$90.50
Purchase #5	$107.59	7.437%	$115.5915	$115.59	$115.60	$115.60
Purchase #6	$196.41	13.548%	$223.0196	$223.02	$223.00	$223.00
Purchase #7	$56.85	4.766%	$59.5595	$59.56	$59.55	$59.60
7 purchase totals =	$771.99		$839.1769	$839.18	$839.15	$839.30