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	$76.65	11.112%	$85.1673	$85.17	$85.15	$85.20
Purchase #2	$225.33	7.346%	$241.8827	$241.88	$241.90	$241.90
Purchase #3	$207.62	6.611%	$221.3458	$221.35	$221.35	$221.30
Purchase #4	$40.57	4.356%	$42.3372	$42.34	$42.35	$42.30
Purchase #5	$240.55	3.562%	$249.1184	$249.12	$249.10	$249.10
Purchase #6	$246.78	6.303%	$262.3345	$262.33	$262.35	$262.30
Purchase #7	$147.27	11.660%	$164.4417	$164.44	$164.45	$164.40
7 purchase totals =	$1,184.77		$1,266.6276	$1,266.63	$1,266.65	$1,266.50