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	$177.44	5.704%	$187.5612	$187.56	$187.55	$187.60
Purchase #2	$127.55	11.520%	$142.2438	$142.24	$142.25	$142.20
Purchase #3	$73.52	5.682%	$77.6974	$77.70	$77.70	$77.70
Purchase #4	$57.25	7.294%	$61.4258	$61.43	$61.45	$61.40
Purchase #5	$37.51	11.278%	$41.7404	$41.74	$41.75	$41.70
Purchase #6	$142.87	3.435%	$147.7776	$147.78	$147.80	$147.80
Purchase #7	$164.77	13.131%	$186.4059	$186.41	$186.40	$186.40
7 purchase totals =	$780.91		$844.8521	$844.86	$844.90	$844.80