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	$107.44	3.289%	$110.9737	$110.97	$110.95	$111.00
Purchase #2	$126.91	8.658%	$137.8979	$137.90	$137.90	$137.90
Purchase #3	$238.42	7.741%	$256.8761	$256.88	$256.90	$256.90
Purchase #4	$250.52	7.822%	$270.1157	$270.12	$270.10	$270.10
Purchase #5	$81.76	10.179%	$90.0824	$90.08	$90.10	$90.10
Purchase #6	$83.92	13.680%	$95.4003	$95.40	$95.40	$95.40
Purchase #7	$85.98	8.834%	$93.5755	$93.58	$93.60	$93.60
7 purchase totals =	$974.95		$1,054.9216	$1,054.93	$1,054.95	$1,055.00