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	$42.98	6.479%	$45.7647	$45.76	$45.75	$45.80
Purchase #2	$221.93	3.221%	$229.0784	$229.08	$229.10	$229.10
Purchase #3	$93.57	3.611%	$96.9488	$96.95	$96.95	$96.90
Purchase #4	$139.98	7.545%	$150.5415	$150.54	$150.55	$150.50
Purchase #5	$35.98	10.826%	$39.8752	$39.88	$39.90	$39.90
Purchase #6	$206.54	9.642%	$226.4546	$226.45	$226.45	$226.50
Purchase #7	$144.66	13.486%	$164.1688	$164.17	$164.15	$164.20
7 purchase totals =	$885.64		$952.8320	$952.83	$952.85	$952.90