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	$98.80	11.578%	$110.2391	$110.24	$110.25	$110.20
Purchase #2	$227.56	4.791%	$238.4624	$238.46	$238.45	$238.50
Purchase #3	$99.52	13.423%	$112.8786	$112.88	$112.90	$112.90
Purchase #4	$107.69	3.228%	$111.1662	$111.17	$111.15	$111.20
Purchase #5	$46.88	9.632%	$51.3955	$51.40	$51.40	$51.40
Purchase #6	$147.51	8.780%	$160.4614	$160.46	$160.45	$160.50
Purchase #7	$233.87	13.492%	$265.4237	$265.42	$265.40	$265.40
7 purchase totals =	$961.83		$1,050.0269	$1,050.03	$1,050.00	$1,050.10