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	$33.51	10.801%	$37.1294	$37.13	$37.15	$37.10
Purchase #2	$39.31	10.278%	$43.3503	$43.35	$43.35	$43.40
Purchase #3	$170.59	4.384%	$178.0687	$178.07	$178.05	$178.10
Purchase #4	$162.86	13.840%	$185.3998	$185.40	$185.40	$185.40
Purchase #5	$180.53	11.664%	$201.587	$201.59	$201.60	$201.60
Purchase #6	$167.53	9.834%	$184.0049	$184.00	$184.00	$184.00
Purchase #7	$104.93	7.615%	$112.9204	$112.92	$112.90	$112.90
7 purchase totals =	$859.26		$942.4605	$942.46	$942.45	$942.50