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	$72.73	6.592%	$77.5244	$77.52	$77.50	$77.50
Purchase #2	$140.48	8.535%	$152.47	$152.47	$152.45	$152.50
Purchase #3	$52.52	11.404%	$58.5094	$58.51	$58.50	$58.50
Purchase #4	$101.88	12.283%	$114.3939	$114.39	$114.40	$114.40
Purchase #5	$207.86	3.720%	$215.5924	$215.59	$215.60	$215.60
Purchase #6	$184.83	6.352%	$196.5704	$196.57	$196.55	$196.60
Purchase #7	$219.57	6.406%	$233.6357	$233.64	$233.65	$233.60
7 purchase totals =	$979.87		$1,048.6962	$1,048.69	$1,048.65	$1,048.70