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	$149.44	3.545%	$154.7376	$154.74	$154.75	$154.70
Purchase #2	$16.46	12.852%	$18.5754	$18.58	$18.60	$18.60
Purchase #3	$89.98	7.553%	$96.7762	$96.78	$96.80	$96.80
Purchase #4	$209.28	11.788%	$233.9499	$233.95	$233.95	$233.90
Purchase #5	$55.69	12.225%	$62.4981	$62.50	$62.50	$62.50
Purchase #6	$118.95	4.150%	$123.8864	$123.89	$123.90	$123.90
Purchase #7	$70.44	11.256%	$78.3687	$78.37	$78.35	$78.40
7 purchase totals =	$710.24		$768.7923	$768.81	$768.85	$768.80