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	$50.47	8.245%	$54.6313	$54.63	$54.65	$54.60
Purchase #2	$90.82	13.327%	$102.9236	$102.92	$102.90	$102.90
Purchase #3	$54.62	5.346%	$57.54	$57.54	$57.55	$57.50
Purchase #4	$117.95	13.760%	$134.1799	$134.18	$134.20	$134.20
Purchase #5	$79.48	12.583%	$89.481	$89.48	$89.50	$89.50
Purchase #6	$86.39	6.864%	$92.3198	$92.32	$92.30	$92.30
Purchase #7	$210.61	8.690%	$228.912	$228.91	$228.90	$228.90
7 purchase totals =	$690.34		$759.9876	$759.98	$760.00	$759.90