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	$248.81	5.224%	$261.8078	$261.81	$261.80	$261.80
Purchase #2	$196.87	13.848%	$224.1326	$224.13	$224.15	$224.10
Purchase #3	$228.32	7.346%	$245.0924	$245.09	$245.10	$245.10
Purchase #4	$23.58	9.411%	$25.7991	$25.80	$25.80	$25.80
Purchase #5	$68.32	4.349%	$71.2912	$71.29	$71.30	$71.30
Purchase #6	$62.25	9.139%	$67.939	$67.94	$67.95	$67.90
Purchase #7	$152.34	8.732%	$165.6423	$165.64	$165.65	$165.60
7 purchase totals =	$980.49		$1,061.7044	$1,061.70	$1,061.75	$1,061.60