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	$155.56	10.276%	$171.5453	$171.55	$171.55	$171.50
Purchase #2	$23.98	5.525%	$25.3049	$25.30	$25.30	$25.30
Purchase #3	$142.79	12.109%	$160.0804	$160.08	$160.10	$160.10
Purchase #4	$180.96	8.710%	$196.7216	$196.72	$196.70	$196.70
Purchase #5	$117.25	12.177%	$131.5275	$131.53	$131.55	$131.50
Purchase #6	$135.82	11.507%	$151.4488	$151.45	$151.45	$151.40
Purchase #7	$239.29	11.794%	$267.5119	$267.51	$267.50	$267.50
7 purchase totals =	$995.65		$1,104.1404	$1,104.14	$1,104.15	$1,104.00