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	$114.56	7.819%	$123.5174	$123.52	$123.50	$123.50
Purchase #2	$84.63	7.189%	$90.7141	$90.71	$90.70	$90.70
Purchase #3	$70.47	3.449%	$72.9005	$72.90	$72.90	$72.90
Purchase #4	$58.36	12.333%	$65.5575	$65.56	$65.55	$65.60
Purchase #5	$6.31	13.803%	$7.181	$7.18	$7.20	$7.20
Purchase #6	$10.42	9.299%	$11.389	$11.39	$11.40	$11.40
Purchase #7	$40.89	13.862%	$46.5582	$46.56	$46.55	$46.60
7 purchase totals =	$385.64		$417.8177	$417.82	$417.80	$417.90