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	$176.92	3.186%	$182.5567	$182.56	$182.55	$182.60
Purchase #2	$165.63	9.701%	$181.6978	$181.70	$181.70	$181.70
Purchase #3	$137.82	13.345%	$156.2121	$156.21	$156.20	$156.20
Purchase #4	$134.75	5.550%	$142.2286	$142.23	$142.25	$142.20
Purchase #5	$14.76	5.284%	$15.5399	$15.54	$15.55	$15.50
Purchase #6	$225.32	10.653%	$249.3233	$249.32	$249.30	$249.30
Purchase #7	$81.48	10.478%	$90.0175	$90.02	$90.00	$90.00
7 purchase totals =	$936.68		$1,017.5759	$1,017.58	$1,017.55	$1,017.50