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	$146.40	9.506%	$160.3168	$160.32	$160.30	$160.30
Purchase #2	$81.45	11.505%	$90.8208	$90.82	$90.80	$90.80
Purchase #3	$207.91	4.280%	$216.8085	$216.81	$216.80	$216.80
Purchase #4	$46.46	13.825%	$52.8831	$52.88	$52.90	$52.90
Purchase #5	$146.92	12.262%	$164.9353	$164.94	$164.95	$164.90
Purchase #6	$225.84	9.819%	$248.0152	$248.02	$248.00	$248.00
Purchase #7	$137.47	9.738%	$150.8568	$150.86	$150.85	$150.90
7 purchase totals =	$992.45		$1,084.6365	$1,084.65	$1,084.60	$1,084.60