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	$34.79	4.296%	$36.2846	$36.28	$36.30	$36.30
Purchase #2	$105.63	3.520%	$109.3482	$109.35	$109.35	$109.30
Purchase #3	$176.90	9.309%	$193.3676	$193.37	$193.35	$193.40
Purchase #4	$63.93	13.217%	$72.3796	$72.38	$72.40	$72.40
Purchase #5	$153.56	4.146%	$159.9266	$159.93	$159.95	$159.90
Purchase #6	$160.37	4.549%	$167.6652	$167.67	$167.65	$167.70
Purchase #7	$72.30	8.366%	$78.3486	$78.35	$78.35	$78.30
7 purchase totals =	$767.48		$817.3204	$817.33	$817.35	$817.30