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	$198.49	12.730%	$223.7578	$223.76	$223.75	$223.80
Purchase #2	$158.99	6.181%	$168.8172	$168.82	$168.80	$168.80
Purchase #3	$41.28	6.472%	$43.9516	$43.95	$43.95	$44.00
Purchase #4	$35.64	13.457%	$40.4361	$40.44	$40.45	$40.40
Purchase #5	$221.40	12.272%	$248.5702	$248.57	$248.55	$248.60
Purchase #6	$168.64	11.125%	$187.4012	$187.40	$187.40	$187.40
Purchase #7	$219.32	10.322%	$241.9582	$241.96	$241.95	$242.00
7 purchase totals =	$1,043.76		$1,154.8923	$1,154.90	$1,154.85	$1,155.00