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	$197.39	11.108%	$219.3161	$219.32	$219.30	$219.30
Purchase #2	$56.99	4.347%	$59.4674	$59.47	$59.45	$59.50
Purchase #3	$157.34	13.413%	$178.444	$178.44	$178.45	$178.40
Purchase #4	$158.62	8.318%	$171.814	$171.81	$171.80	$171.80
Purchase #5	$225.54	5.663%	$238.3123	$238.31	$238.30	$238.30
Purchase #6	$167.32	6.650%	$178.4468	$178.45	$178.45	$178.40
Purchase #7	$164.72	10.294%	$181.6763	$181.68	$181.70	$181.70
7 purchase totals =	$1,127.92		$1,227.4769	$1,227.48	$1,227.45	$1,227.40