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	$50.97	3.261%	$52.6321	$52.63	$52.65	$52.60
Purchase #2	$11.72	10.448%	$12.9445	$12.94	$12.95	$12.90
Purchase #3	$92.44	7.224%	$99.1179	$99.12	$99.10	$99.10
Purchase #4	$52.48	10.307%	$57.8891	$57.89	$57.90	$57.90
Purchase #5	$202.64	6.316%	$215.4387	$215.44	$215.45	$215.40
Purchase #6	$224.41	3.867%	$233.0879	$233.09	$233.10	$233.10
Purchase #7	$103.37	5.701%	$109.2631	$109.26	$109.25	$109.30
7 purchase totals =	$738.03		$780.3733	$780.37	$780.40	$780.30