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	$171.39	4.535%	$179.1625	$179.16	$179.15	$179.20
Purchase #2	$200.78	4.318%	$209.4497	$209.45	$209.45	$209.40
Purchase #3	$171.50	6.465%	$182.5875	$182.59	$182.60	$182.60
Purchase #4	$53.97	3.865%	$56.0559	$56.06	$56.05	$56.10
Purchase #5	$148.74	10.410%	$164.2238	$164.22	$164.20	$164.20
Purchase #6	$227.31	3.256%	$234.7112	$234.71	$234.70	$234.70
Purchase #7	$27.38	13.467%	$31.0673	$31.07	$31.05	$31.10
7 purchase totals =	$1,001.07		$1,057.2579	$1,057.26	$1,057.20	$1,057.30