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	$26.68	5.167%	$28.0586	$28.06	$28.05	$28.10
Purchase #2	$112.94	10.148%	$124.4012	$124.40	$124.40	$124.40
Purchase #3	$131.59	6.850%	$140.6039	$140.60	$140.60	$140.60
Purchase #4	$238.95	13.541%	$271.3062	$271.31	$271.30	$271.30
Purchase #5	$154.93	7.743%	$166.9262	$166.93	$166.95	$166.90
Purchase #6	$250.91	7.319%	$269.2741	$269.27	$269.25	$269.30
Purchase #7	$61.71	4.253%	$64.3345	$64.33	$64.35	$64.30
7 purchase totals =	$977.71		$1,064.9047	$1,064.90	$1,064.90	$1,064.90