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	$127.73	3.141%	$131.742	$131.74	$131.75	$131.70
Purchase #2	$106.96	3.810%	$111.0352	$111.04	$111.05	$111.00
Purchase #3	$237.33	11.217%	$263.9513	$263.95	$263.95	$264.00
Purchase #4	$192.65	12.804%	$217.3169	$217.32	$217.30	$217.30
Purchase #5	$144.40	4.740%	$151.2446	$151.24	$151.25	$151.20
Purchase #6	$228.98	7.671%	$246.5451	$246.55	$246.55	$246.50
Purchase #7	$140.83	10.469%	$155.5735	$155.57	$155.55	$155.60
7 purchase totals =	$1,178.88		$1,277.4086	$1,277.41	$1,277.40	$1,277.30