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	$58.91	4.432%	$61.5209	$61.52	$61.50	$61.50
Purchase #2	$204.77	8.473%	$222.1202	$222.12	$222.10	$222.10
Purchase #3	$219.72	9.357%	$240.2792	$240.28	$240.30	$240.30
Purchase #4	$204.64	8.773%	$222.5931	$222.59	$222.60	$222.60
Purchase #5	$45.64	13.221%	$51.6741	$51.67	$51.65	$51.70
Purchase #6	$87.28	9.376%	$95.4634	$95.46	$95.45	$95.50
Purchase #7	$168.69	7.850%	$181.9322	$181.93	$181.95	$181.90
7 purchase totals =	$989.65		$1,075.5831	$1,075.57	$1,075.55	$1,075.60