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	$91.92	5.269%	$96.7633	$96.76	$96.75	$96.80
Purchase #2	$100.88	10.280%	$111.2505	$111.25	$111.25	$111.30
Purchase #3	$201.53	6.781%	$215.1957	$215.20	$215.20	$215.20
Purchase #4	$213.70	6.383%	$227.3405	$227.34	$227.35	$227.30
Purchase #5	$123.50	4.174%	$128.6549	$128.65	$128.65	$128.70
Purchase #6	$18.38	11.775%	$20.5442	$20.54	$20.55	$20.50
Purchase #7	$97.86	3.528%	$101.3125	$101.31	$101.30	$101.30
7 purchase totals =	$847.77		$901.0616	$901.05	$901.05	$901.10