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	$180.53	5.834%	$191.0621	$191.06	$191.05	$191.10
Purchase #2	$35.86	12.243%	$40.2503	$40.25	$40.25	$40.30
Purchase #3	$84.88	13.650%	$96.4661	$96.47	$96.45	$96.50
Purchase #4	$250.46	3.651%	$259.6043	$259.60	$259.60	$259.60
Purchase #5	$197.62	4.689%	$206.8864	$206.89	$206.90	$206.90
Purchase #6	$5.31	12.782%	$5.9887	$5.99	$6.00	$6.00
Purchase #7	$57.68	3.650%	$59.7853	$59.79	$59.80	$59.80
7 purchase totals =	$812.34		$860.0432	$860.05	$860.05	$860.20