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	$241.81	9.768%	$265.43	$265.43	$265.45	$265.40
Purchase #2	$36.83	9.776%	$40.4305	$40.43	$40.45	$40.40
Purchase #3	$31.93	4.225%	$33.279	$33.28	$33.30	$33.30
Purchase #4	$124.80	7.685%	$134.3909	$134.39	$134.40	$134.40
Purchase #5	$171.46	5.304%	$180.5542	$180.55	$180.55	$180.60
Purchase #6	$246.52	9.594%	$270.1711	$270.17	$270.15	$270.20
Purchase #7	$145.48	3.494%	$150.5631	$150.56	$150.55	$150.60
7 purchase totals =	$998.83		$1,074.8188	$1,074.81	$1,074.85	$1,074.90