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	$69.34	12.523%	$78.0234	$78.02	$78.00	$78.00
Purchase #2	$62.32	6.394%	$66.3047	$66.30	$66.30	$66.30
Purchase #3	$196.87	11.830%	$220.1597	$220.16	$220.15	$220.20
Purchase #4	$167.80	8.598%	$182.2274	$182.23	$182.25	$182.20
Purchase #5	$187.98	4.623%	$196.6703	$196.67	$196.65	$196.70
Purchase #6	$187.77	3.329%	$194.0209	$194.02	$194.00	$194.00
Purchase #7	$165.33	12.372%	$185.7846	$185.78	$185.80	$185.80
7 purchase totals =	$1,037.41		$1,123.1910	$1,123.18	$1,123.15	$1,123.20