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	$59.73	13.154%	$67.5869	$67.59	$67.60	$67.60
Purchase #2	$117.96	7.766%	$127.1208	$127.12	$127.10	$127.10
Purchase #3	$41.62	11.225%	$46.2918	$46.29	$46.30	$46.30
Purchase #4	$141.82	3.338%	$146.554	$146.55	$146.55	$146.60
Purchase #5	$160.47	6.812%	$171.4012	$171.40	$171.40	$171.40
Purchase #6	$194.68	6.336%	$207.0149	$207.01	$207.00	$207.00
Purchase #7	$82.52	4.747%	$86.4372	$86.44	$86.45	$86.40
7 purchase totals =	$798.80		$852.4068	$852.40	$852.40	$852.40