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	$180.87	7.272%	$194.0229	$194.02	$194.00	$194.00
Purchase #2	$101.81	9.105%	$111.0798	$111.08	$111.10	$111.10
Purchase #3	$18.77	6.836%	$20.0531	$20.05	$20.05	$20.10
Purchase #4	$143.42	11.737%	$160.2532	$160.25	$160.25	$160.30
Purchase #5	$234.88	12.138%	$263.3897	$263.39	$263.40	$263.40
Purchase #6	$202.43	3.297%	$209.1041	$209.10	$209.10	$209.10
Purchase #7	$122.88	6.684%	$131.0933	$131.09	$131.10	$131.10
7 purchase totals =	$1,005.06		$1,088.9961	$1,088.98	$1,089.00	$1,089.10