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	$204.64	5.437%	$215.7663	$215.77	$215.75	$215.80
Purchase #2	$222.69	12.150%	$249.7468	$249.75	$249.75	$249.70
Purchase #3	$112.55	12.637%	$126.7729	$126.77	$126.75	$126.80
Purchase #4	$241.79	3.641%	$250.5936	$250.59	$250.60	$250.60
Purchase #5	$40.60	5.635%	$42.8878	$42.89	$42.90	$42.90
Purchase #6	$85.66	3.722%	$88.8483	$88.85	$88.85	$88.80
Purchase #7	$225.32	12.590%	$253.6878	$253.69	$253.70	$253.70
7 purchase totals =	$1,133.25		$1,228.3035	$1,228.31	$1,228.30	$1,228.30