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	$112.84	9.139%	$123.1524	$123.15	$123.15	$123.20
Purchase #2	$69.49	9.380%	$76.0082	$76.01	$76.00	$76.00
Purchase #3	$24.58	7.639%	$26.4577	$26.46	$26.45	$26.50
Purchase #4	$94.89	7.495%	$102.002	$102.00	$102.00	$102.00
Purchase #5	$136.61	10.647%	$151.1549	$151.15	$151.15	$151.20
Purchase #6	$174.63	7.240%	$187.2732	$187.27	$187.25	$187.30
Purchase #7	$120.89	11.403%	$134.6751	$134.68	$134.70	$134.70
7 purchase totals =	$733.93		$800.7235	$800.72	$800.70	$800.90