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	$176.41	5.440%	$186.0067	$186.01	$186.00	$186.00
Purchase #2	$109.44	3.412%	$113.1741	$113.17	$113.15	$113.20
Purchase #3	$152.73	6.373%	$162.4635	$162.46	$162.45	$162.50
Purchase #4	$226.73	9.179%	$247.5415	$247.54	$247.55	$247.50
Purchase #5	$250.69	10.603%	$277.2707	$277.27	$277.25	$277.30
Purchase #6	$158.44	5.694%	$167.4616	$167.46	$167.45	$167.50
Purchase #7	$95.57	5.408%	$100.7384	$100.74	$100.75	$100.70
7 purchase totals =	$1,170.01		$1,254.6565	$1,254.65	$1,254.60	$1,254.70