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	$75.25	4.541%	$78.6671	$78.67	$78.65	$78.70
Purchase #2	$20.35	4.470%	$21.2596	$21.26	$21.25	$21.30
Purchase #3	$228.86	7.328%	$245.6309	$245.63	$245.65	$245.60
Purchase #4	$149.74	4.349%	$156.2522	$156.25	$156.25	$156.30
Purchase #5	$198.49	5.696%	$209.796	$209.80	$209.80	$209.80
Purchase #6	$99.54	9.174%	$108.6718	$108.67	$108.65	$108.70
Purchase #7	$230.54	13.136%	$260.8237	$260.82	$260.80	$260.80
7 purchase totals =	$1,002.77		$1,081.1013	$1,081.10	$1,081.05	$1,081.20