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	$66.56	8.145%	$71.9813	$71.98	$72.00	$72.00
Purchase #2	$171.51	8.681%	$186.3988	$186.40	$186.40	$186.40
Purchase #3	$78.64	4.708%	$82.3424	$82.34	$82.35	$82.30
Purchase #4	$56.39	6.855%	$60.2555	$60.26	$60.25	$60.30
Purchase #5	$124.46	7.223%	$133.4497	$133.45	$133.45	$133.40
Purchase #6	$114.53	4.421%	$119.5934	$119.59	$119.60	$119.60
Purchase #7	$10.44	4.379%	$10.8972	$10.90	$10.90	$10.90
7 purchase totals =	$622.53		$664.9183	$664.92	$664.95	$664.90