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	$120.65	5.817%	$127.6682	$127.67	$127.65	$127.70
Purchase #2	$158.80	3.522%	$164.3929	$164.39	$164.40	$164.40
Purchase #3	$79.95	10.645%	$88.4607	$88.46	$88.45	$88.50
Purchase #4	$40.29	12.515%	$45.3323	$45.33	$45.35	$45.30
Purchase #5	$143.62	3.121%	$148.1024	$148.10	$148.10	$148.10
Purchase #6	$184.80	12.310%	$207.5489	$207.55	$207.55	$207.50
Purchase #7	$44.49	4.224%	$46.3693	$46.37	$46.35	$46.40
7 purchase totals =	$772.60		$827.8747	$827.87	$827.85	$827.90