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	$52.99	8.810%	$57.6584	$57.66	$57.65	$57.70
Purchase #2	$126.75	7.330%	$136.0408	$136.04	$136.05	$136.00
Purchase #3	$103.95	7.238%	$111.4739	$111.47	$111.45	$111.50
Purchase #4	$220.54	6.465%	$234.7979	$234.80	$234.80	$234.80
Purchase #5	$224.70	7.853%	$242.3457	$242.35	$242.35	$242.30
Purchase #6	$93.35	6.629%	$99.5382	$99.54	$99.55	$99.50
Purchase #7	$162.36	13.672%	$184.5579	$184.56	$184.55	$184.60
7 purchase totals =	$984.64		$1,066.4128	$1,066.42	$1,066.40	$1,066.40