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	$228.40	6.264%	$242.707	$242.71	$242.70	$242.70
Purchase #2	$60.85	7.840%	$65.6206	$65.62	$65.60	$65.60
Purchase #3	$91.88	4.508%	$96.022	$96.02	$96.00	$96.00
Purchase #4	$169.58	12.595%	$190.9386	$190.94	$190.95	$190.90
Purchase #5	$173.60	4.111%	$180.7367	$180.74	$180.75	$180.70
Purchase #6	$225.54	8.690%	$245.1394	$245.14	$245.15	$245.10
Purchase #7	$80.28	11.373%	$89.4102	$89.41	$89.40	$89.40
7 purchase totals =	$1,030.13		$1,110.5745	$1,110.58	$1,110.55	$1,110.40