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	$132.73	6.482%	$141.3336	$141.33	$141.35	$141.30
Purchase #2	$55.99	12.323%	$62.8896	$62.89	$62.90	$62.90
Purchase #3	$182.98	5.450%	$192.9524	$192.95	$192.95	$193.00
Purchase #4	$218.46	11.422%	$243.4125	$243.41	$243.40	$243.40
Purchase #5	$40.76	11.196%	$45.3235	$45.32	$45.30	$45.30
Purchase #6	$105.96	3.537%	$109.7078	$109.71	$109.70	$109.70
Purchase #7	$171.67	5.652%	$181.3728	$181.37	$181.35	$181.40
7 purchase totals =	$908.55		$976.9922	$976.98	$976.95	$977.00