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	$89.32	4.499%	$93.3385	$93.34	$93.35	$93.30
Purchase #2	$227.66	9.598%	$249.5108	$249.51	$249.50	$249.50
Purchase #3	$40.88	6.240%	$43.4309	$43.43	$43.45	$43.40
Purchase #4	$98.82	8.443%	$107.1634	$107.16	$107.15	$107.20
Purchase #5	$81.65	9.757%	$89.6166	$89.62	$89.60	$89.60
Purchase #6	$213.29	4.773%	$223.4703	$223.47	$223.45	$223.50
Purchase #7	$189.54	9.265%	$207.1009	$207.10	$207.10	$207.10
7 purchase totals =	$941.16		$1,013.6314	$1,013.63	$1,013.60	$1,013.60