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	$59.46	6.669%	$63.4254	$63.43	$63.45	$63.40
Purchase #2	$59.42	3.303%	$61.3826	$61.38	$61.40	$61.40
Purchase #3	$60.74	3.202%	$62.6849	$62.68	$62.70	$62.70
Purchase #4	$90.89	8.607%	$98.7129	$98.71	$98.70	$98.70
Purchase #5	$64.48	4.141%	$67.1501	$67.15	$67.15	$67.20
Purchase #6	$186.98	9.646%	$205.0161	$205.02	$205.00	$205.00
Purchase #7	$145.76	5.115%	$153.2156	$153.22	$153.20	$153.20
7 purchase totals =	$667.73		$711.5876	$711.59	$711.60	$711.60