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	$62.40	8.620%	$67.7789	$67.78	$67.80	$67.80
Purchase #2	$247.28	6.493%	$263.3359	$263.34	$263.35	$263.30
Purchase #3	$137.77	3.511%	$142.6071	$142.61	$142.60	$142.60
Purchase #4	$72.74	10.234%	$80.1842	$80.18	$80.20	$80.20
Purchase #5	$169.25	11.539%	$188.7798	$188.78	$188.80	$188.80
Purchase #6	$245.69	7.506%	$264.1315	$264.13	$264.15	$264.10
Purchase #7	$44.96	3.757%	$46.6491	$46.65	$46.65	$46.60
7 purchase totals =	$980.09		$1,053.4665	$1,053.47	$1,053.55	$1,053.40