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	$202.53	10.379%	$223.5506	$223.55	$223.55	$223.60
Purchase #2	$106.57	11.185%	$118.4899	$118.49	$118.50	$118.50
Purchase #3	$41.47	5.844%	$43.8935	$43.89	$43.90	$43.90
Purchase #4	$141.26	10.849%	$156.5853	$156.59	$156.60	$156.60
Purchase #5	$76.39	11.674%	$85.3078	$85.31	$85.30	$85.30
Purchase #6	$42.31	3.159%	$43.6466	$43.65	$43.65	$43.60
Purchase #7	$89.82	4.397%	$93.7694	$93.77	$93.75	$93.80
7 purchase totals =	$700.35		$765.2431	$765.25	$765.25	$765.30