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	$130.57	11.536%	$145.6326	$145.63	$145.65	$145.60
Purchase #2	$149.53	9.725%	$164.0718	$164.07	$164.05	$164.10
Purchase #3	$62.92	3.823%	$65.3254	$65.33	$65.35	$65.30
Purchase #4	$190.54	4.587%	$199.2801	$199.28	$199.30	$199.30
Purchase #5	$107.71	4.564%	$112.6259	$112.63	$112.65	$112.60
Purchase #6	$170.96	11.781%	$191.1008	$191.10	$191.10	$191.10
Purchase #7	$20.46	5.178%	$21.5194	$21.52	$21.50	$21.50
7 purchase totals =	$832.69		$899.5560	$899.56	$899.60	$899.50