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	$155.54	5.649%	$164.3265	$164.33	$164.35	$164.30
Purchase #2	$199.91	7.714%	$215.3311	$215.33	$215.35	$215.30
Purchase #3	$35.47	10.652%	$39.2483	$39.25	$39.25	$39.20
Purchase #4	$227.28	7.565%	$244.4737	$244.47	$244.45	$244.50
Purchase #5	$165.90	4.455%	$173.2908	$173.29	$173.30	$173.30
Purchase #6	$79.87	6.320%	$84.9178	$84.92	$84.90	$84.90
Purchase #7	$113.82	12.298%	$127.8176	$127.82	$127.80	$127.80
7 purchase totals =	$977.79		$1,049.4058	$1,049.41	$1,049.40	$1,049.30