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	$47.40	5.144%	$49.8383	$49.84	$49.85	$49.80
Purchase #2	$244.70	13.360%	$277.3919	$277.39	$277.40	$277.40
Purchase #3	$187.37	3.189%	$193.3452	$193.35	$193.35	$193.30
Purchase #4	$218.33	13.656%	$248.1451	$248.15	$248.15	$248.10
Purchase #5	$79.97	3.240%	$82.561	$82.56	$82.55	$82.60
Purchase #6	$81.33	9.638%	$89.1686	$89.17	$89.15	$89.20
Purchase #7	$62.60	12.619%	$70.4995	$70.50	$70.50	$70.50
7 purchase totals =	$921.70		$1,010.9496	$1,010.96	$1,010.95	$1,010.90