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	$244.34	4.146%	$254.4703	$254.47	$254.45	$254.50
Purchase #2	$215.36	4.409%	$224.8552	$224.86	$224.85	$224.90
Purchase #3	$242.70	11.437%	$270.4576	$270.46	$270.45	$270.50
Purchase #4	$48.61	12.502%	$54.6872	$54.69	$54.70	$54.70
Purchase #5	$125.79	4.553%	$131.5172	$131.52	$131.50	$131.50
Purchase #6	$98.97	4.153%	$103.0802	$103.08	$103.10	$103.10
Purchase #7	$186.45	3.272%	$192.5506	$192.55	$192.55	$192.60
7 purchase totals =	$1,162.22		$1,231.6183	$1,231.63	$1,231.60	$1,231.80