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	$62.87	6.807%	$67.1496	$67.15	$67.15	$67.10
Purchase #2	$85.68	8.712%	$93.1444	$93.14	$93.15	$93.10
Purchase #3	$198.52	11.706%	$221.7588	$221.76	$221.75	$221.80
Purchase #4	$245.94	5.185%	$258.692	$258.69	$258.70	$258.70
Purchase #5	$103.30	6.488%	$110.0021	$110.00	$110.00	$110.00
Purchase #6	$123.86	5.673%	$130.8866	$130.89	$130.90	$130.90
Purchase #7	$123.75	11.764%	$138.308	$138.31	$138.30	$138.30
7 purchase totals =	$943.92		$1,019.9415	$1,019.94	$1,019.95	$1,019.90