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	$218.51	12.368%	$245.5353	$245.54	$245.55	$245.50
Purchase #2	$152.28	12.393%	$171.1521	$171.15	$171.15	$171.20
Purchase #3	$147.77	12.736%	$166.59	$166.59	$166.60	$166.60
Purchase #4	$179.86	9.508%	$196.9611	$196.96	$196.95	$197.00
Purchase #5	$122.47	7.830%	$132.0594	$132.06	$132.05	$132.10
Purchase #6	$148.73	12.376%	$167.1368	$167.14	$167.15	$167.10
Purchase #7	$174.77	8.587%	$189.7775	$189.78	$189.80	$189.80
7 purchase totals =	$1,144.39		$1,269.2122	$1,269.22	$1,269.25	$1,269.30