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	$183.48	11.464%	$204.5141	$204.51	$204.50	$204.50
Purchase #2	$119.92	9.770%	$131.6362	$131.64	$131.65	$131.60
Purchase #3	$206.49	7.443%	$221.8591	$221.86	$221.85	$221.90
Purchase #4	$102.73	9.337%	$112.3219	$112.32	$112.30	$112.30
Purchase #5	$198.82	6.261%	$211.2681	$211.27	$211.25	$211.30
Purchase #6	$50.83	7.755%	$54.7719	$54.77	$54.75	$54.80
Purchase #7	$185.94	3.349%	$192.1671	$192.17	$192.15	$192.20
7 purchase totals =	$1,048.21		$1,128.5384	$1,128.54	$1,128.45	$1,128.60