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	$70.35	7.183%	$75.4032	$75.40	$75.40	$75.40
Purchase #2	$86.45	12.104%	$96.9139	$96.91	$96.90	$96.90
Purchase #3	$25.48	11.572%	$28.4285	$28.43	$28.45	$28.40
Purchase #4	$130.27	11.606%	$145.3891	$145.39	$145.40	$145.40
Purchase #5	$13.81	3.693%	$14.32	$14.32	$14.30	$14.30
Purchase #6	$100.50	4.567%	$105.0898	$105.09	$105.10	$105.10
Purchase #7	$174.91	3.718%	$181.4132	$181.41	$181.40	$181.40
7 purchase totals =	$601.77		$646.9577	$646.95	$646.95	$646.90