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	$135.94	3.230%	$140.3309	$140.33	$140.35	$140.30
Purchase #2	$12.33	7.478%	$13.252	$13.25	$13.25	$13.30
Purchase #3	$204.80	3.464%	$211.8943	$211.89	$211.90	$211.90
Purchase #4	$134.52	13.599%	$152.8134	$152.81	$152.80	$152.80
Purchase #5	$53.34	11.411%	$59.4266	$59.43	$59.45	$59.40
Purchase #6	$107.28	6.260%	$113.9957	$114.00	$114.00	$114.00
Purchase #7	$52.50	6.624%	$55.9776	$55.98	$56.00	$56.00
7 purchase totals =	$700.71		$747.6905	$747.69	$747.75	$747.70