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	$173.47	6.774%	$185.2209	$185.22	$185.20	$185.20
Purchase #2	$63.36	12.853%	$71.5037	$71.50	$71.50	$71.50
Purchase #3	$211.95	10.618%	$234.4549	$234.45	$234.45	$234.50
Purchase #4	$245.98	3.808%	$255.3469	$255.35	$255.35	$255.30
Purchase #5	$191.75	5.343%	$201.9952	$202.00	$202.00	$202.00
Purchase #6	$90.90	13.587%	$103.2506	$103.25	$103.25	$103.30
Purchase #7	$92.46	13.648%	$105.0789	$105.08	$105.10	$105.10
7 purchase totals =	$1,069.87		$1,156.8511	$1,156.85	$1,156.85	$1,156.90