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	$130.70	8.317%	$141.5703	$141.57	$141.55	$141.60
Purchase #2	$180.91	3.423%	$187.1025	$187.10	$187.10	$187.10
Purchase #3	$234.31	3.589%	$242.7194	$242.72	$242.70	$242.70
Purchase #4	$154.81	10.811%	$171.5465	$171.55	$171.55	$171.50
Purchase #5	$181.63	5.309%	$191.2727	$191.27	$191.25	$191.30
Purchase #6	$177.59	3.762%	$184.2709	$184.27	$184.25	$184.30
Purchase #7	$71.89	9.199%	$78.5032	$78.50	$78.50	$78.50
7 purchase totals =	$1,131.84		$1,196.9855	$1,196.98	$1,196.90	$1,197.00