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	$230.75	4.324%	$240.7276	$240.73	$240.75	$240.70
Purchase #2	$59.34	5.227%	$62.4417	$62.44	$62.45	$62.40
Purchase #3	$71.73	9.462%	$78.5171	$78.52	$78.50	$78.50
Purchase #4	$57.36	13.207%	$64.9355	$64.94	$64.95	$64.90
Purchase #5	$11.41	9.816%	$12.53	$12.53	$12.55	$12.50
Purchase #6	$56.32	4.287%	$58.7344	$58.73	$58.75	$58.70
Purchase #7	$61.39	10.461%	$67.812	$67.81	$67.80	$67.80
7 purchase totals =	$548.30		$585.6983	$585.70	$585.75	$585.50