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	$30.43	9.687%	$33.3778	$33.38	$33.40	$33.40
Purchase #2	$209.90	4.427%	$219.1923	$219.19	$219.20	$219.20
Purchase #3	$27.81	12.809%	$31.3722	$31.37	$31.35	$31.40
Purchase #4	$53.31	11.652%	$59.5217	$59.52	$59.50	$59.50
Purchase #5	$169.62	10.344%	$187.1655	$187.17	$187.15	$187.20
Purchase #6	$193.85	6.144%	$205.7601	$205.76	$205.75	$205.80
Purchase #7	$44.35	5.169%	$46.6425	$46.64	$46.65	$46.60
7 purchase totals =	$729.27		$783.0321	$783.03	$783.00	$783.10