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	$126.45	12.545%	$142.3132	$142.31	$142.30	$142.30
Purchase #2	$248.63	6.746%	$265.4026	$265.40	$265.40	$265.40
Purchase #3	$204.36	11.382%	$227.6203	$227.62	$227.60	$227.60
Purchase #4	$163.70	6.798%	$174.8283	$174.83	$174.85	$174.80
Purchase #5	$98.54	12.749%	$111.1029	$111.10	$111.10	$111.10
Purchase #6	$152.77	13.556%	$173.4795	$173.48	$173.50	$173.50
Purchase #7	$209.76	11.809%	$234.5306	$234.53	$234.55	$234.50
7 purchase totals =	$1,204.21		$1,329.2774	$1,329.27	$1,329.30	$1,329.20