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	$22.43	11.454%	$24.9991	$25.00	$25.00	$25.00
Purchase #2	$205.64	3.516%	$212.8703	$212.87	$212.85	$212.90
Purchase #3	$149.76	10.173%	$164.9951	$165.00	$165.00	$165.00
Purchase #4	$143.40	10.437%	$158.3667	$158.37	$158.35	$158.40
Purchase #5	$167.80	10.701%	$185.7563	$185.76	$185.75	$185.80
Purchase #6	$72.87	10.728%	$80.6875	$80.69	$80.70	$80.70
Purchase #7	$64.47	11.484%	$71.8737	$71.87	$71.85	$71.90
7 purchase totals =	$826.37		$899.5487	$899.56	$899.50	$899.70