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	$164.88	12.719%	$185.8511	$185.85	$185.85	$185.90
Purchase #2	$181.64	5.598%	$191.8082	$191.81	$191.80	$191.80
Purchase #3	$38.91	9.860%	$42.7465	$42.75	$42.75	$42.70
Purchase #4	$167.77	6.501%	$178.6767	$178.68	$178.70	$178.70
Purchase #5	$69.94	10.241%	$77.1026	$77.10	$77.10	$77.10
Purchase #6	$174.90	7.441%	$187.9143	$187.91	$187.90	$187.90
Purchase #7	$141.56	8.706%	$153.8842	$153.88	$153.90	$153.90
7 purchase totals =	$939.60		$1,017.9836	$1,017.98	$1,018.00	$1,018.00