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	$112.69	9.440%	$123.3279	$123.33	$123.35	$123.30
Purchase #2	$199.68	11.621%	$222.8848	$222.88	$222.90	$222.90
Purchase #3	$170.78	4.664%	$178.7452	$178.75	$178.75	$178.70
Purchase #4	$131.30	8.463%	$142.4119	$142.41	$142.40	$142.40
Purchase #5	$105.27	5.781%	$111.3557	$111.36	$111.35	$111.40
Purchase #6	$62.44	7.374%	$67.0443	$67.04	$67.05	$67.00
Purchase #7	$213.26	3.451%	$220.6196	$220.62	$220.60	$220.60
7 purchase totals =	$995.42		$1,066.3894	$1,066.39	$1,066.40	$1,066.30