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	$43.87	11.760%	$49.0291	$49.03	$49.05	$49.00
Purchase #2	$46.36	6.705%	$49.4684	$49.47	$49.45	$49.50
Purchase #3	$118.88	10.292%	$131.1151	$131.12	$131.10	$131.10
Purchase #4	$38.54	10.559%	$42.6094	$42.61	$42.60	$42.60
Purchase #5	$62.56	4.477%	$65.3608	$65.36	$65.35	$65.40
Purchase #6	$184.92	7.543%	$198.8685	$198.87	$198.85	$198.90
Purchase #7	$139.26	6.814%	$148.7492	$148.75	$148.75	$148.70
7 purchase totals =	$634.39		$685.2005	$685.21	$685.15	$685.20