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	$188.71	4.329%	$196.8793	$196.88	$196.90	$196.90
Purchase #2	$38.75	12.506%	$43.5961	$43.60	$43.60	$43.60
Purchase #3	$193.39	6.241%	$205.4595	$205.46	$205.45	$205.50
Purchase #4	$111.35	4.721%	$116.6068	$116.61	$116.60	$116.60
Purchase #5	$18.72	13.304%	$21.2105	$21.21	$21.20	$21.20
Purchase #6	$126.48	4.399%	$132.0439	$132.04	$132.05	$132.00
Purchase #7	$58.71	12.637%	$66.1292	$66.13	$66.15	$66.10
7 purchase totals =	$736.11		$781.9253	$781.93	$781.95	$781.90