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	$214.71	3.839%	$222.9527	$222.95	$222.95	$223.00
Purchase #2	$163.47	9.754%	$179.4149	$179.41	$179.40	$179.40
Purchase #3	$70.41	11.350%	$78.4015	$78.40	$78.40	$78.40
Purchase #4	$48.45	8.570%	$52.6022	$52.60	$52.60	$52.60
Purchase #5	$166.30	6.385%	$176.9183	$176.92	$176.90	$176.90
Purchase #6	$38.87	12.272%	$43.6401	$43.64	$43.65	$43.60
Purchase #7	$85.62	7.171%	$91.7598	$91.76	$91.75	$91.80
7 purchase totals =	$787.83		$845.6895	$845.68	$845.65	$845.70