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	$244.55	12.642%	$275.466	$275.47	$275.45	$275.50
Purchase #2	$132.77	7.468%	$142.6853	$142.69	$142.70	$142.70
Purchase #3	$156.75	7.267%	$168.141	$168.14	$168.15	$168.10
Purchase #4	$182.89	11.651%	$204.1985	$204.20	$204.20	$204.20
Purchase #5	$83.32	7.360%	$89.4524	$89.45	$89.45	$89.50
Purchase #6	$173.67	4.454%	$181.4053	$181.41	$181.40	$181.40
Purchase #7	$177.98	12.705%	$200.5924	$200.59	$200.60	$200.60
7 purchase totals =	$1,151.93		$1,261.9409	$1,261.95	$1,261.95	$1,262.00