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	$143.84	8.506%	$156.075	$156.08	$156.10	$156.10
Purchase #2	$154.61	13.658%	$175.7266	$175.73	$175.75	$175.70
Purchase #3	$5.77	10.255%	$6.3617	$6.36	$6.35	$6.40
Purchase #4	$98.98	12.229%	$111.0843	$111.08	$111.10	$111.10
Purchase #5	$125.83	13.826%	$143.2273	$143.23	$143.25	$143.20
Purchase #6	$183.85	9.229%	$200.8175	$200.82	$200.80	$200.80
Purchase #7	$39.51	12.782%	$44.5602	$44.56	$44.55	$44.60
7 purchase totals =	$752.39		$837.8526	$837.86	$837.90	$837.90