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	$193.93	13.633%	$220.3685	$220.37	$220.35	$220.40
Purchase #2	$181.28	3.456%	$187.545	$187.55	$187.55	$187.50
Purchase #3	$188.60	3.108%	$194.4617	$194.46	$194.45	$194.50
Purchase #4	$156.85	11.241%	$174.4815	$174.48	$174.50	$174.50
Purchase #5	$180.47	6.311%	$191.8595	$191.86	$191.85	$191.90
Purchase #6	$21.54	12.686%	$24.2726	$24.27	$24.25	$24.30
Purchase #7	$118.79	10.387%	$131.1287	$131.13	$131.15	$131.10
7 purchase totals =	$1,041.46		$1,124.1175	$1,124.12	$1,124.10	$1,124.20