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	$230.86	11.832%	$258.1754	$258.18	$258.20	$258.20
Purchase #2	$75.54	9.701%	$82.8681	$82.87	$82.85	$82.90
Purchase #3	$91.60	6.681%	$97.7198	$97.72	$97.70	$97.70
Purchase #4	$221.77	10.800%	$245.7212	$245.72	$245.70	$245.70
Purchase #5	$248.69	10.619%	$275.0984	$275.10	$275.10	$275.10
Purchase #6	$35.92	12.294%	$40.336	$40.34	$40.35	$40.30
Purchase #7	$83.49	3.760%	$86.6292	$86.63	$86.65	$86.60
7 purchase totals =	$987.87		$1,086.5481	$1,086.56	$1,086.55	$1,086.50